fix(resolution): resolve same-named methods to the call site's own file (#1079)

[colbymchenry]

Closes #1079.

Problem

When two files each declared a same-named class with a same-named method — class Logger { void log(); } in both a/svc and b/svc — a call resolved to whichever definition happened to be indexed first. So a call in b/ wrongly pointed at a/'s method, mixing up that method's callers and blast radius.

@inth3shadows reported this for C++ instance calls and diagnosed it precisely: resolveMethodOnType only disambiguated multiple matches when a Java/Kotlin import FQN was present (#314), and every other language fell through to matches[0].

Scope — it's a cross-language pattern, not one site

Validating "are other languages affected?" with two-file repros surfaced the same "pick the first-indexed, ignore the call site's file" pattern in three distinct resolution paths, each firing for a different call shape:

Call shape	Firing path	Affected (confirmed)
obj.log() — instance	resolveMethodOnType	C++
Logger.log() — class receiver	matchMethodCall Strategy 1/2/3	Python, TypeScript, Java, C#
Logger::log() — qualified	matchByQualifiedName	C++, Rust

(The plain instance case only resolves to a method in C++ today — other languages don't infer a local variable's type, so they produced no edge rather than a wrong one. Constructor / instantiates resolution and the general name-match path were already file-aware via path proximity, which is why only these method paths were affected.)

Fix

One shared helper — preferCallSiteFile(nodes, callSiteFile) — prefers a candidate declared in the call site's own file when a name is ambiguous, and is a no-op when there are fewer than two candidates or none share the file. Applied at all five sites (resolveMethodOnType, both branches of matchByQualifiedName, and matchMethodCall Strategies 1/2/3).

In resolveMethodOnType it runs after the preferredFqn block, so Java/Kotlin import disambiguation (#314) — whose target is intentionally in another file — is unaffected.

Tests

8 tests under Same-name method disambiguation (#1079): the preferCallSiteFile contract, resolveMethodOnType precedence (including a guard that an import FQN still beats the same-file preference, #314), matchByQualifiedName disambiguation, and end-to-end index tests for the C++ instance, TypeScript static, and C++ qualified call shapes. Full suite green (1905 passed).

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