v0.22.1 — dogfood loop fixes

Five bug fixes from a 5-round structured dogfood pass. All fixes converge on
one root pattern: the test/prod source classification was implemented in five
sites independently, and result truncation in centralized_compress was
biased against production callers when source data ordering put tests at
the array head/tail.

Fixes

• get_ast_node called_by post-truncation bias (src/mcp/server/tools/ast_node.rs)
  When include_references=true include_tests=true, SQL row order without
  ORDER BY clustered test callers at array start/end, and centralized_compress
  kept first 10 + last 5 — leaving zero production callers visible for
  test-heavy targets like conn (49 prod / 76 test). Stable-sort prod-first
  inside the tool before emitting.

• find_references references post-truncation bias (src/mcp/server/tools/refs.rs)
  Same pattern as above, but worse because find_references defaults
  include_tests=true (rename audits need test sites). 125-caller targets
  collapsed to a 10-prod-of-cli + 5-tests-of-tests/ window with all
  src/indexer/, src/mcp/, src/storage/ prod callers silently dropped.
  Same prod-first stable sort inside the tool.

• module_overview caller_count includes test sources (src/storage/queries/routes.rs)
  get_module_exports cc LEFT JOIN counted every incoming calls edge —
  did not filter source-side is_test. parse_code showed caller_count=39
  while find_references include_tests=false / get_ast_node impact /
  project_map hot_functions all reported 0 prod. Aligned with the four
  other prod-only counts via the same source-side filter pattern.

• ast_search ranking includes test sources (src/storage/queries/nodes.rs)
  get_nodes_with_files_by_filters ORDER BY (SELECT COUNT(*) FROM edges …)
  ranked test-only utility wrappers (e.g. extract_relations 0 prod / 64 test)
  above genuinely hot prod symbols. Same source-side filter applied.

• find_references "Symbol not found" for test/bench symbols (src/mcp/server/tools/refs.rs)
  resolve_fuzzy_name filters test/bench candidates upstream; previous error
  said "not found" even when the symbol was present. Re-query without the
  filter to detect the "found-but-filtered" case and surface a bypass hint
  with the actual file paths. Unblocks the dead-code → find_references
  reverse-trace flow.

Internal refactor

src/storage/queries/{routes,nodes,project_map}.rs now share a single
SQL filter via src/domain.rs::prod_source_join_sql() +
PROD_SOURCE_FILTER_AND / TEST_SOURCE_FILTER_OR. Five duplicate LIKE
chains collapsed to one canonical source. New test/harness directory
conventions only need a single edit going forward.

Tests

• tests/mcp_stdio_integration.rs (new, 245 LOC) — three end-to-end JSON-RPC
  stdio tests against a real spawned code-graph-mcp serve subprocess.
  Covers prod-first sort survival across centralized_compress truncation,
  caller_count prod-only correctness, and the new explanatory error message.
  Caught a real gap in the error-message fix during authoring (the
  FuzzyResolution::NotFound branch needed the same treatment as
  Unique).
• cargo test --release: 299 lib + 3 new mcp_stdio_integration + ~194 other
  integration = 496 total, 0 failed (1 pre-existing #[ignore]).
• cargo +1.95.0 clippy --no-default-features -- -D warnings clean.
• cargo +1.95.0 clippy --all-targets -- -D warnings clean.

Full Changelog: v0.22.0...v0.22.1