feat(extraction): add Erlang language support (.erl/.hrl) (#635, #648) (#1165)

Vendored WhatsApp/tree-sitter-erlang 0.19 (the ELP grammar, ABI 14) with an
Erlang-shaped extractor: multi-clause/multi-arity functions merged into one
symbol, -spec signatures, records with fields, -type/-opaque aliases, -define
macros, -include/-include_lib file edges, and -export-driven visibility.

Modules wrap in a namespace so remote mod:fn(...) calls resolve through the
existing qualified-name matcher as mod::fn with zero resolver changes.
-behaviour declarations link to the behaviour module — gated to namespace
targets only (bare-name fallthrough linked -behaviour(supervisor) to an
unrelated macro constant on emqx). OTP indirection with static targets is
followed: spawn/apply/proc_lib/timer/rpc MFA-argument callees, and
gen_server:call/cast(?MODULE | ?SERVER) to the module's own
handle_call/handle_cast. Var-module dispatch and message sends stay
deliberately unlinked. codegraph_explore also normalizes Erlang-native query
spelling (mod:fn/3, init/2) so named symbols resolve as typed.

Benchmarked on cowboy (189 files), ejabberd (414), emqx (2,447): extraction
PASS on all three; with-codegraph arms reached 2/2/0 file Reads vs 10/5+/19
without, fastest on the largest repo.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

src/resolution/name-matcher.ts

@@ -1753,6 +1753,26 @@ export function matchReference(
     return matchFunctionRef(ref, context);
   }
 
+  // Erlang `-behaviour(m)` refs target a MODULE. Letting them fall through to
+  // bare-name matching grabs any same-named symbol — on emqx,
+  // `-behaviour(supervisor)` resolved to a `-define(supervisor, …)` macro
+  // constant in an unrelated app. Resolve only to the behaviour module's
+  // namespace; an out-of-repo behaviour (OTP's gen_server/supervisor) stays
+  // unresolved rather than guessed.
+  if (ref.language === 'erlang' && ref.referenceKind === 'implements') {
+    const modules = context
+      .getNodesByName(ref.referenceName)
+      .filter((n) => n.language === 'erlang' && n.kind === 'namespace');
+    const chosen = preferCallSiteFile(modules, ref.filePath)[0];
+    if (!chosen) return null;
+    return {
+      original: ref,
+      targetNodeId: chosen.id,
+      confidence: 0.9,
+      resolvedBy: 'exact-match',
+    };
+  }
+
   // Try strategies in order of confidence
   let result: ResolvedRef | null;