Fix unresolved exact caller identity fallback

DEVELOPER_GUIDE.md

@@ -1706,15 +1706,29 @@ index paths to replace older physical-path target keys before identity-aware rea
 C# common member names are never discarded during extraction. The writer persists their
 receiver/type evidence in `target_qualifier`, and reference finalization records
 `resolution_state`. Bare-name `references` and unqualified graph discovery remain broad and
-retain the stored resolution labels. On a current reference-identity contract, however, exact
-qualified C# `callers` queries and confirmed `impact` traversal require a `resolved` or
-`resolved_group` candidate that matches one of the selected definition IDs or its resolved
-polymorphic-dispatch family; unresolved or ambiguous same-leaf evidence remains inspectable but
-cannot become a confirmed caller edge.
+retain the stored resolution labels. On a current C# reference-identity contract, however,
+exact C# `callers` queries and confirmed C# `impact` traversal require a `resolved` or
+`resolved_group` candidate that matches one of the selected definition IDs, including the
+resolved polymorphic-dispatch family. Multiple C#
+same-name definitions contribute their resolved ID union; unresolved or ambiguous same-leaf
+evidence remains inspectable but cannot become a confirmed caller edge or transitive hop. When
+no matching definition ID exists, exact callers and impact return zero confirmed rows instead
+of traversing the name fallback. CLI/MCP payloads expose `identity_root_available`,
+`identity_root_unavailable_reason`, `graph_evidence_confidence`, and
+`identity_root_resolution_truncated`; missing roots and capped identity sets set
+`authoritative_count: false`, while impact marks a missing root heuristic and strict mode fails
+through the stable `no_identity_backed_root` failure code. Legacy or stale identity contracts
+may keep the name-based compatibility path, but must label it `name_fallback`, degraded, and
+non-authoritative.
+Other graph languages retain their existing language-specific exact matching until they expose
+the same persisted target-identity contract. When `--lang` is omitted, impact partitions the
+same traversal step: C# rows must match resolved candidate IDs, while non-C# rows retain their
+language-specific exact-name graph. A root inferred only from non-C# definitions reports
+`language_graph`; persisted reference-graph incompleteness makes every impact count
+non-authoritative even when the local traversal and identity resolution are otherwise complete.
 C# callable hotspots likewise count logical target identities instead of leaf-name aggregates.
 Candidate groups contribute only when they collapse to one logical target, name, and kind, and
-unresolved rows do not inflate the confirmed count. Legacy or stale identity contracts keep the
-name-based compatibility path. The CLI `--include-qualified-common-calls` flag and MCP
+unresolved rows do not inflate the confirmed count. The CLI `--include-qualified-common-calls` flag and MCP
 `includeQualifiedCommonCalls` argument still bypass the query-time common-member noise filter.
 Keep dependency edges identity-scoped: completeness options may expose unresolved evidence but
 must not convert it into a same-name file dependency.
@@ -5761,14 +5775,26 @@ identity-aware read を ready にする前に、full、scoped、no-op、削除
 C# の一般的な member 名は extraction 時に破棄しません。writer は receiver / 型の evidence を
 `target_qualifier` に永続化し、reference finalization は `resolution_state` を記録します。bare-name の
 `references` と無修飾 graph discovery は広い検索結果と保存済み resolution label を維持します。一方、
-現行の reference-identity contract では、exact qualified C# `callers` query と confirmed `impact`
-traversal は、選択した definition ID のいずれかに一致する `resolved` または `resolved_group` candidate
-か、その解決済み polymorphic-dispatch family を必須とします。未解決または曖昧な same-leaf evidence
-は引き続き確認できますが、confirmed caller edge にはなりません。C# callable hotspot も
+現行の C# reference-identity contract では、exact C# `callers` query と confirmed C#
+`impact` traversal は、選択した definition ID または解決済み polymorphic-dispatch family の
+いずれかに一致する `resolved` または `resolved_group` candidate を必須とします。C# の同名 definition
+が複数ある場合は解決済み ID の和集合を対象にしますが、未解決または
+曖昧な same-leaf evidence は引き続き確認できても confirmed caller edge や推移 hop にはなりません。
+一致する definition ID が無い場合、exact callers と impact は name fallback を走査せず confirmed 0 件を
+返します。CLI/MCP payload は `identity_root_available`、`identity_root_unavailable_reason`、
+`graph_evidence_confidence`、`identity_root_resolution_truncated` を公開し、root 不在または identity 集合の
+cap 到達では `authoritative_count: false` を設定します。impact は root 不在を heuristic とし、strict mode は
+安定した `no_identity_backed_root` failure code で失敗します。legacy または stale な identity contract が
+名前ベースの互換経路を維持する場合も、`name_fallback`、degraded、non-authoritative と明示しなければなりません。
+他の graph 言語は、同等の永続 target-identity contract を公開するまで既存の言語固有 exact matching を維持します。
+`--lang` を省略した場合、impact は同じ traversal step を分割し、C# row には解決済み candidate ID の
+一致を必須とする一方、非 C# row では言語固有の exact-name graph を維持します。非 C# definition だけから
+推論した root は `language_graph` と明示し、永続 reference graph が incomplete なら、局所 traversal と
+identity resolution が完了していてもすべての impact count を non-authoritative とします。
+C# callable hotspot も
 leaf-name aggregate ではなく logical target identity を
 集計し、candidate group は logical target、name、kind が 1 つに収束するときだけ加算し、unresolved
-row は confirmed count を増やしません。legacy または stale な identity contract は名前ベースの
-互換経路を維持します。CLI の `--include-qualified-common-calls` と MCP の
+row は confirmed count を増やしません。CLI の `--include-qualified-common-calls` と MCP の
 `includeQualifiedCommonCalls` は、引き続き query-time common-member noise filter を無効化します。
 dependency edge は identity scope のままにし、completeness option で未解決 evidence を公開しても、
 同名の file dependency へ変換してはいけません。

TESTING_GUIDE.md

@@ -213,6 +213,7 @@ Candidate-ordered parallel-index recovery tests must prove that the fatal result
   Reusable-stat snapshot semantics keep one valid row beside two rows from the same stale extractor language plus NULL, text, integer, and invalid-timestamp stat storage, so malformed-row filtering and cached stale-language rejection remain one contract.
   Graph-kind regressions keep default canonical `call` / `instantiate` / `subscribe` output, raw-kind output, and explicit non-default kind access in the same seeded fixture so filtering and projection cannot drift apart.
   Caller-ranking coverage keeps the large count-over-path-category case, primary-recipe ties, multi-path filtering, test exclusion, and offset page reconstruction in one seeded `DbReaderTests` fixture. CLI human/JSON and MCP pagination assertions reuse compact two- or three-caller fixtures and require the structured ranking recipe to match the ordering applied before pagination (#4881).
+  Exact C# caller-root coverage is coordinated across `DbReaderIssue5183Tests`, `QueryCommandRunnerIssue5183Tests`, and `McpServerIssue5183Tests`. Keep one isolated fixture with an unresolved external call whose definition file is omitted, a resolved local target sharing its leaf name, two unrelated resolved same-name methods, an unresolved transitive chain, mixed C#/Python callers, a non-C#-only root colliding with an unresolved C# call, and complete, capped, plus persisted-incomplete traversal states. Assert that broad references/callers retain `name_discovery` evidence while exact callers, inspect summaries, impact, hotspots, CLI JSON/compact, and MCP confirmed counts accept only resolved C# target IDs without dropping non-C# language-graph edges; missing roots and incomplete graphs must expose stable degraded/non-authoritative metadata and strict impact failure (#5183, regression boundary from #5084).
   Query-only regression fixtures run representative `status`, `search`, and `files` commands against a checkpointed WAL database copied without sidecars and assert that the database, `-wal`, and `-shm` artifact set plus persistent pragmas remain unchanged. Separate fixtures prove that committed hot-WAL content, empty-to-hot transitions, checkpoint resets, cross-database dependency targets, and long-lived LSP refreshes use cleaned-up generation-validated private snapshots without touching source sidecars. Cross-database coverage also pins disposal ordering and snapshot-directory cleanup, while injected persistent copy failures pin the non-retrying `query_only_snapshot_copy_failed` taxonomy; interrupted-batch readiness demotion is covered separately through explicit `Repair` intent.
   `DatabasePermissionPolicyTests.cs` injects a file-mode provider so unsupported and access-denied Unix mode operations remain deterministic and cross-platform while proving both best-effort diagnostics and strict remediation failures.
   `DbSchemaConstraintTests.cs` also locks schema constraints to `SymbolKindCatalog` and required file foreign keys so DB readiness checks fail when code enums and SQLite CHECK clauses drift.
@@ -1349,6 +1350,7 @@ dotnet test --filter "FullyQualifiedName~GitHelperTests"
   再利用 stat snapshot の意味論は、有効な1行、同じ stale extractor 言語の2行、NULL / text / integer / 不正 timestamp の stat storage を同居させ、malformed row の除外と stale-language 判定の false cache を1つの契約として固定します。
   graph kind の回帰では、既定 canonical `call` / `instantiate` / `subscribe` 出力、raw-kind 出力、明示的な非既定 kind access を同じ seed 済み fixture にまとめ、filtering と projection のずれを検出します。
   caller ranking の coverage では、count と path category に大差がある場合、primary recipe の同順位、複数 path filter、test 除外、offset page の再構成を1つの seed 済み `DbReaderTests` fixture にまとめます。CLI の human / JSON と MCP pagination の assertion は2～3 caller の小さな fixture を再利用し、structured ranking recipe が pagination 前に適用した順序と一致することを必須とします (#4881)。
+  exact C# caller root の coverage は `DbReaderIssue5183Tests`、`QueryCommandRunnerIssue5183Tests`、`McpServerIssue5183Tests` で連携します。definition file を省略した未解決 external call、同じ leaf 名を持つ解決済み local target、互いに無関係な同名 method 2 件、未解決 root の背後にある推移 chain、C# / Python 混合 caller、未解決 C# call と衝突する非 C# 専用 root、complete / capped / 永続 incomplete の traversal 状態を1つの隔離 fixture に維持してください。broad references/callers は `name_discovery` evidence を保つ一方、exact callers、inspect summary、impact、hotspots、CLI JSON / compact、MCP の confirmed count は解決済み C# target ID だけを受理し、非 C# の language-graph edge を落とさないことを確認します。root 不在と incomplete graph では安定した degraded / non-authoritative metadata と strict impact failure を返すことを assertion にします（#5183、#5084 からの回帰境界）。
   query-only の回帰 fixture では sidecar なしで copy した checkpoint 済み WAL database に対して代表的な `status`、`search`、`files` command を実行し、database、`-wal`、`-shm` の artifact set と永続 pragma が変化しないことを検証します。別の fixture では committed hot-WAL content、empty-to-hot transition、checkpoint reset、cross-database dependency target、長時間 LSP refresh が、source sidecar に触れず cleanup される generation 検証済み private snapshot を使うことを固定します。cross-database coverage は dispose 順序と snapshot directory cleanup も固定し、注入した永続的 copy failure は retry されない `query_only_snapshot_copy_failed` taxonomy を固定します。interrupted batch の readiness demotion は明示的な `Repair` intent の別テストで固定します。
   `DatabasePermissionPolicyTests.cs` は file-mode provider を注入し、unsupported / access-denied な Unix mode 操作を deterministic かつ cross-platform に保ちながら、best-effort diagnostic と strict remediation failure の両方を検証します。
   `DbSchemaConstraintTests.cs` は DB readiness check が code enum と SQLite CHECK 句の drift を検出できるよう、schema constraint と `SymbolKindCatalog`、必須 file foreign key の同期も固定します。