feat(resolution): Erlang behaviour-callback dispatch synthesizer (#635, #648) (#1166)

Bridges the OTP callback boundary: a framework call through a variable
module — cowboy's Handler:init / Middleware:execute folds, a plugin
manager's Mod:callback(...) — now links to the repo's implementers of the
behaviour declaring that callback, so codegraph_explore connects flows
end-to-end across behaviour dispatch instead of stopping at it.

Precision gates: the callback arity must match the site, exactly one
in-repo behaviour may declare that (name, arity) — a collision bails
(cowboy's init/2 is declared by five handler-flavored behaviours and
correctly stays silent) — the implementer must export the callback, and
above the fan-out cap the site is skipped entirely (ejabberd's gen_mod
with ~230 implementers stays a visibly dynamic boundary). Behaviour
discovery scans -callback declarations in every module so implementer-less
behaviours still gate ambiguity. Edges carry provenance:'heuristic' with
synthesizedBy:'erlang-behaviour' and the wiring site, rendered as dynamic
dispatch in explore.

Validated per the dispatch-family playbook: cowboy 38 edges (middleware
chain, stream-handler folds, sub-protocol upgrade), ejabberd 598, emqx 843;
36/36 sampled edges precise (target declares the via-behaviour and exports
the callback); node counts unchanged; ~1.4s added on emqx's 2,273 files;
zero-control clean. The cowboy request flow connects in one explore call.

Includes an Erlang comment stripper (%-comments, string/atom/$-char aware)
for the dispatch-site scans.

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

src/resolution/strip-comments.ts

@@ -35,7 +35,8 @@ export type CommentLang =
   | 'go'
   | 'rust'
   | 'c'
-  | 'cpp';
+  | 'cpp'
+  | 'erlang';
 
 export function stripCommentsForRegex(content: string, lang: CommentLang): string {
   switch (lang) {
@@ -45,6 +46,8 @@ export function stripCommentsForRegex(content: string, lang: CommentLang): strin
       return stripRuby(content);
     case 'rust':
       return stripRust(content);
+    case 'erlang':
+      return stripErlang(content);
     case 'php':
       return stripPhp(content);
     case 'go':
@@ -471,3 +474,55 @@ function stripRust(src: string): string {
 
   return out.join('');
 }
+
+// ---------- Erlang ----------
+
+/**
+ * Erlang: `%` starts a line comment unless it sits inside a `"string"`, a
+ * `'quoted atom'`, or is the character literal `$%`. Strings and quoted atoms
+ * are left intact (a behaviour callback name can be a quoted atom); only the
+ * comment text is blanked.
+ */
+function stripErlang(src: string): string {
+  const out = src.split('');
+  let i = 0;
+  const n = src.length;
+
+  while (i < n) {
+    const c = src[i];
+
+    if (c === '"' || c === "'") {
+      const quote = c;
+      i++;
+      while (i < n && src[i] !== quote) {
+        if (src[i] === '\\' && i + 1 < n) {
+          i += 2;
+          continue;
+        }
+        i++;
+      }
+      if (i < n) i++;
+      continue;
+    }
+
+    // Character literal: `$x`, `$\n`, `$%` — the next char (or escape) is data.
+    if (c === '$') {
+      i++;
+      if (i < n && src[i] === '\\') i++;
+      i++;
+      continue;
+    }
+
+    if (c === '%') {
+      let end = i;
+      while (end < n && src[end] !== '\n') end++;
+      blankRange(out, i, end, src);
+      i = end;
+      continue;
+    }
+
+    i++;
+  }
+
+  return out.join('');
+}