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>

README.md

@@ -244,7 +244,7 @@ The reliable, universal payoff is **surgical context and speed**: CodeGraph coll
 | **Full-Text Search** | Find code by name instantly across your entire codebase, powered by FTS5 |
 | **Impact Analysis** | Trace callers, callees, and the full impact radius of any symbol before making changes |
 | **Always Fresh** | File watcher uses native OS events (FSEvents/inotify/ReadDirectoryChangesW) with debounced auto-sync — the graph stays current as you code, zero config |
-| **20+ Languages** | TypeScript, JavaScript, Python, Go, Rust, Java, C#, VB.NET, PHP, Ruby, C, C++, Objective-C, Metal, Swift, Kotlin, Scala, Dart, Lua, Luau, R, CFML, COBOL, Svelte, Vue, Astro, Liquid, Pascal/Delphi |
+| **20+ Languages** | TypeScript, JavaScript, Python, Go, Rust, Java, C#, VB.NET, PHP, Ruby, C, C++, Objective-C, Metal, Swift, Kotlin, Scala, Dart, Lua, Luau, R, Erlang, CFML, COBOL, Svelte, Vue, Astro, Liquid, Pascal/Delphi |
 | **Framework-aware Routes** | Recognizes web-framework routing files and links URL patterns to their handlers across 17 frameworks |
 | **Mixed iOS / React Native / Expo** | Closes cross-language flows that static parsing misses: Swift ↔ ObjC bridging, React Native legacy bridge + TurboModules + Fabric view components, native → JS event emitters, Expo Modules |
 | **100% Local** | No data leaves your machine. No API keys. No external services. SQLite database only |
@@ -718,6 +718,7 @@ is written):
 | CFML | `.cfc`, `.cfm`, `.cfs` | Full support (tag-based `<cfcomponent>`/`<cffunction>` and bare-script `component { ... }` styles, `extends`/`implements`, embedded `<cfscript>` delegation, call edges) |
 | COBOL | `.cbl`, `.cob`, `.cpy` | Full support (programs, sections/paragraphs with PERFORM/GO TO call edges, CALL 'literal' cross-program calls, COPY copybook imports — including standalone `.cpy` files — DATA DIVISION records/fields/88-levels, EXEC CICS LINK/XCTL and EXEC SQL INCLUDE targets; fixed and free format) |
 | Visual Basic .NET | `.vb` | Full support (classes, Modules, interfaces, structures, enums, properties, events, `Declare` P/Invoke, `Handles`/`WithEvents`, `Inherits`/`Implements` edges, call edges through VB's call/index paren ambiguity, `As New` instantiation, interpolated strings, LINQ, Unicode identifiers) |
+| Erlang | `.erl`, `.hrl` | Full support (functions with multi-clause/multi-arity grouping, `-spec` signatures, records with fields, `-type`/`-opaque` aliases, `-define` macros, `-include`/`-include_lib`/`-import` edges, local and `mod:fn` remote call edges, `fun name/arity` references, `spawn`/`apply`/`proc_lib`/`timer`/`rpc` MFA-argument call edges, `gen_server:call/cast(?MODULE)` → own `handle_call`/`handle_cast` links, `-behaviour` links, `-export`-based visibility) |
 
 ## Measured cross-file coverage