fix: resolve Solidity qualified library calls Lib.fn() (AGE-5)

[saldestechnology]

Stacked on #29 (AGE-4). Base is the AGE-4 branch so the diff shows only the AGE-5 change; retarget to main once #29 merges.

Summary

Solidity qualified calls LibraryName.fn(...) (e.g. ChessPureLib.isKingInCheck(...)) were captured as edges but frequently left unresolved (target_id = NULL) whenever the bare function name existed in ≥2 files (e.g. a Solidity library and a TypeScript mirror). Since fan_in/fan_out/complexity/reachability count only resolved edges, the callee's metrics silently collapsed to 0 — corrupting hotspots ranking, query callers/impact, and any reachability closure. Higher severity than the sibling Solidity issues because it silently corrupts existing metrics rather than omitting a feature.

Root cause (two drop points)

1. Qualifier discarded at capture — the MemberAccess arm of extract_calls_from_expr kept only member.name and threw away the ChessPureLib object; the edge stored the bare name with context: None.
2. Ambiguity bail in the resolver — resolve_edge_targets's unique-name step only resolves when the bare target_name matches exactly one symbol; ambiguous names were left NULL. No step consulted the qualifier or qualified_name.

Fix

• Parser (src/parser/solidity.rs): for Name.member(...) calls, store the fully qualified Name.member in the edge's context (kept target_name = bare name for fallback and get_incoming_edges). Complex/chained receivers stay unqualified. Same treatment for block-style calls.
• Resolver (src/db/schema.rs): new Step 0 resolves an edge whose context equals a symbol's qualified_name exactly (Solidity library methods already carry qualified_name = "ChessPureLib.isKingInCheck"), when unique. Ordered before the existing substring-LIKE step so the exact match wins and later target_id IS NULL steps skip the row — no regression to other languages' resolution (verified: the LIKE step keeps its target_id IS NULL guard).

The optional same-language tiebreak for unqualified ambiguous names was deferred (would risk cross-language behavior changes; the exact-qualified step resolves the reported cases).

Tests

test_solidity_qualified_call_resolves_across_ambiguous_bare_name: two libraries define isKingInCheck (ambiguous, COUNT=2) and a caller does ChessPureLib.isKingInCheck(...); asserts the edge resolves target_id to the correct library method, not NULL and not the other file's symbol.

• cargo fmt --all -- --check ✅
• cargo clippy --all-targets -- -D warnings ✅ (0 warnings)
• cargo test ✅ (304 lib + all integration suites, 0 failures)

Refs AGE-5. Depends on #29 (AGE-4).