fix(#1223): install scripts/fix-slash-commands.cjs so gsd-tools loads (#1240)

* fix(#1223): install scripts/fix-slash-commands.cjs so gsd-tools loads

Before this fix, bin/install.js copied scripts/changeset/ and scripts/lib/
into the runtime config dir but omitted scripts/fix-slash-commands.cjs.
gsd-core/bin/lib/command-roster.cjs requires this file at module load via
require('../../../scripts/fix-slash-commands.cjs'), so every gsd-tools
command crashed with MODULE_NOT_FOUND on every installed runtime.

Four changes:
- bin/install.js copy step: copy fix-slash-commands.cjs into <configDir>/scripts/
  with source-missing hard-fail and verifyFileInstalled smoke check
- bin/install.js writeManifest: track scripts/fix-slash-commands.cjs (not
  covered by the changeset/lib subdir loops)
- bin/install.js uninstall: best-effort unlinkSync before scripts/ rmdir
- scripts/fix-slash-commands.cjs readCmdNames(): wrap readdirSync in
  try/catch returning [] so skill-based/global installs without a local
  commands/gsd/ directory do not throw ENOENT

Tests added to tests/install.test.cjs (6 new tests):
- smoke: install() copies fix-slash-commands.cjs
- e2e: spawned gsd-tools.cjs does not crash with MODULE_NOT_FOUND
- manifest: writeManifest() tracks the file
- uninstall: uninstall() removes the file
- readCmdNames unit: export returns an array
- readCmdNames spawn: absent COMMANDS_DIR returns exit 0 (no throw)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* chore(#1223): backfill changeset PR number (#1240)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

scripts/fix-slash-commands.cjs

@@ -92,9 +92,21 @@ function transformContentToHyphen(src, cmdNames) {
 }
 
 function readCmdNames() {
-  return fs.readdirSync(COMMANDS_DIR)
-    .filter(f => f.endsWith('.md'))
-    .map(f => f.replace(/\.md$/, ''));
+  try {
+    return fs.readdirSync(COMMANDS_DIR)
+      .filter(f => f.endsWith('.md'))
+      .map(f => f.replace(/\.md$/, ''));
+  } catch (err) {
+    // Only swallow the missing-directory case. Any other error (EACCES, ENOTDIR,
+    // etc.) indicates a real misconfiguration and must propagate so callers are
+    // not silently handed an empty registry while the real problem goes undetected.
+    if (err.code !== 'ENOENT') throw err;
+    // COMMANDS_DIR may not exist on installs that use skill-based runtimes or
+    // global Claude installs (no local commands/gsd/ directory). Return [] so
+    // callers that handle an empty array gracefully (buildPattern returns null,
+    // transformContent is a no-op) are not broken by a missing directory.
+    return [];
+  }
 }
 
 function processFile(file, cmdNames) {