Fix Live accept for Elixir templates in lib/ (#374)

* Fix Live accept for Elixir templates in lib/

Wrap and accept search the repo for impeccable variant markers. That
search skipped .ex files and the lib/ tree, so Phoenix LiveView markup
inside ~H""" blocks never matched and browser Accept returned
"Session markers not found".

Extend the same EXTENSIONS and searchDirs in live-accept.mjs and
live-wrap.mjs. Add a regression test that accepts from
lib/my_app_web/components/layouts.ex.

* Live: give the source search one owner for template extensions

The #374 fix had to patch the same hardcoded EXTENSIONS array in two
files because live-wrap.mjs and live-accept.mjs each carried their own
copy of the project source walk. The copies had already drifted: same
extension list twice, same searchDirs twice, and one realpathSync
guarded by try/catch while the other was not.

Meanwhile hook-lib.mjs had solved this properly for the design hook in
#316/#347 with a configurable `detector.extensions` and suffix matching
that handles .blade.php and .html.erb. Live never read it, so a project
that taught the hook about .heex still got 'Session markers not found'
on Accept.

- lib/template-extensions.mjs is the single owner. It holds Live's
  built-in markup list, the suffix matcher, and the detector.extensions
  config reader. hook-lib.mjs now imports its normalize/merge/match
  helpers from here instead of duplicating them, and re-exports
  matchConfiguredExtension for its existing callers.
- Live resolves built-ins PLUS detector.extensions, so teaching the hook
  about a server template teaches wrap and accept at the same time.
- live/source-search.mjs holds the walk both scripts share. Callers pass
  the one thing that actually differs (skipDirs, fileFilter). Unifying
  gives live-wrap the guarded realpathSync, so a dangling symlink in the
  tree no longer throws out of the whole wrap, and makes it skip
  .impeccable artifacts the way accept already did.
- Extensions are matched on filename suffix rather than path.extname, so
  root.html.heex and show.html.erb resolve.
- Drop .exs. Those are Elixir scripts (mix.exs, config/*.exs), never
  markup, and including them only lets a wrap query match build config.
- Fill the Elixir gap in the manual-edit paths, which kept their own
  allowlists and would have left Live half-working for Phoenix:
  live-commit-manual-edits.mjs and live-manual-edit-evidence.mjs.

Verified the round trip by hand against a Phoenix layout: wrap injects
markers into a ~H""" block in lib/**/*.ex, accept carbonizes the chosen
variant back out.

AI assistance: written with Claude Code.

Co-Authored-By: Claude <noreply@anthropic.com>

---------

Co-authored-by: Nils Kanevad <heliumbrain@users.noreply.github.com>
Co-authored-by: Paul Bakaus <paul.bakaus@gmail.com>
Co-authored-by: Claude <noreply@anthropic.com>

skill/scripts/hook-lib.mjs

@@ -42,6 +42,16 @@ import path from 'node:path';
 import { pathToFileURL, fileURLToPath } from 'node:url';
 import { extractPlatform, loadContext } from './context.mjs';
 import { IMPECCABLE_COMMAND } from './lib/provider.mjs';
+// `detector.extensions` (issue #316) is shared with Live's source search, which
+// needs the same answer for `.heex` / `.blade.php` when it hunts for session
+// markers. lib/template-extensions.mjs owns the shape; re-exported here because
+// hook-lib has been the import site for matchConfiguredExtension since #347.
+import {
+  matchConfiguredExtension,
+  mergeExtensions,
+} from './lib/template-extensions.mjs';
+
+export { matchConfiguredExtension };
 
 const __filename = fileURLToPath(import.meta.url);
 const __dirname = path.dirname(__filename);
@@ -263,49 +273,6 @@ function applyDetectorConfigSource(config, raw) {
   return config;
 }
 
-// Extra scanned extensions from `detector.extensions` config. Entries are
-// `{ ext, engine }` (engine 'html' | 'text', default 'html' — the common case
-// for server-side templates) or bare strings as shorthand. Extensions are
-// matched against the end of the filename, not path.extname, so double
-// extensions like `.blade.php` and `.html.erb` work (issue #316).
-function normalizeExtensionEntries(entries) {
-  if (!Array.isArray(entries)) return [];
-  const out = [];
-  for (const entry of entries) {
-    const raw = typeof entry === 'string' ? entry : entry?.ext;
-    if (typeof raw !== 'string') continue;
-    let ext = raw.trim().toLowerCase();
-    if (!ext) continue;
-    if (!ext.startsWith('.')) ext = `.${ext}`;
-    const engine = (!(typeof entry === 'string') && entry?.engine === 'text') ? 'text' : 'html';
-    out.push({ ext, engine });
-  }
-  return out;
-}
-
-function mergeExtensions(existing, incoming) {
-  const map = new Map();
-  for (const entry of normalizeExtensionEntries(existing)) map.set(entry.ext, entry);
-  for (const entry of normalizeExtensionEntries(incoming)) map.set(entry.ext, entry);
-  return Array.from(map.values());
-}
-
-export function matchConfiguredExtension(filePath, extensions) {
-  if (!Array.isArray(extensions) || extensions.length === 0) return null;
-  const name = path.basename(String(filePath || '')).toLowerCase();
-  if (!name) return null;
-  // The longest matching suffix wins, so `.blade.php` beats a broader `.php`
-  // entry regardless of config order.
-  let best = null;
-  for (const entry of normalizeExtensionEntries(extensions)) {
-    if (name.length > entry.ext.length && name.endsWith(entry.ext)
-      && (!best || entry.ext.length > best.ext.length)) {
-      best = entry;
-    }
-  }
-  return best;
-}
-
 function applyConfigSource(config, raw) {
   if (!raw || typeof raw !== 'object') return config;
   if (Object.prototype.hasOwnProperty.call(raw, 'enabled')) {