fix(walker): catch Js.Exn in pattern position + exempt phase2c.res fixture

Two bugs blocked Phase 2c parity tests + governance:

1. `walker-phase2c-parity / untyped-exception on lines 19/22/28` failed
   with missing=[22]. Tree-sitter labels `Js.Exn.Error(_)` in catch-arm
   pattern position with a different node type than the typed branches
   ([member_expression]/[value_identifier_path]) the detector matches.
   Add a leaf-only text fallback ( <=32 chars, no children) so any
   small leaf carrying `Js.Exn` / `Promise.catch` flags too. Dedupe by
   (kind, line) collapses same-line duplicates against the parent
   try_expression hit, so no over-reporting.

2. `governance / Language / package anti-pattern policy` failed with
   "❌ ReScript files detected" for the new phase2c.res fixture. The
   walker exists precisely to detect anti-patterns in .res files, so
   the fixture is intentional. Side-channel exemption in
   `.hypatia-ignore` (same pattern as the existing `sample.res` line)
   per `feedback_inline_pragma_vs_snapshot_test`.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

.hypatia-ignore

@@ -23,3 +23,4 @@
 # exemption avoids touching the file content. See feedback memory
 # `feedback_inline_pragma_vs_snapshot_test` for the general principle.
 cicd_rules/banned_language_file:tools/res-to-affine/test/fixtures/sample.res
+cicd_rules/banned_language_file:tools/res-to-affine/test/fixtures/phase2c.res

tools/res-to-affine/walker.ml

@@ -421,7 +421,22 @@ let detect_untyped_exception ~source acc node =
       in
       if hits_js_exn || hits_promise_catch then push acc
       else acc
-  | _ -> acc
+  | _ ->
+      (* Tree-sitter labels module paths differently depending on syntactic
+         position — `Js.Exn.Error(_)` in a catch-arm pattern is not a
+         [member_expression]/[value_identifier_path], so the typed branches
+         above miss it. Fall back to a tight leaf-only text match so the
+         pattern still flags. The master walker's [dedupe] collapses any
+         same-line duplicate against the [try_expression] hit. *)
+      if node.children = [] then
+        let text = node_text ~source node in
+        if String.length text <= 32
+           && (starts_with "Js.Exn" text
+               || text = "Promise.catch"
+               || ends_with ".Promise.catch" text)
+        then push acc
+        else acc
+      else acc
 
 (* ---- mutable-global: top-level [let x = ref(...)] or top-level [:=] ---- *)