fix(#947): restore gsd- prefix on Hermes skills for canonical dispatch (#955)

* test(#947): add regression tests and update stale Hermes assertions

- Add bug-947-hermes-gsd-prefix.test.cjs: 12 TDD tests covering fresh
  install canonical layout, bare-stem migration, manifest key format,
  and non-Hermes runtime isolation
- Update hermes-skills-migration.test.cjs: bare-stem → gsd-prefixed
  path and name assertions (#947 canonical layout)
- Update install-nested-layout.test.cjs: Hermes NEST matrix prefix ''
  → 'gsd-'
- Update install-regressions.test.cjs: Defect #1 now seeds bare-stem
  dirs (help/, quick/) and asserts gsd-help/ canonical output; use
  real GSD stems so readGsdCommandNames() migration finds them
- Update install-runtime-artifacts.test.cjs: Hermes nested layout and
  legacy migration assertions align with gsd- prefix
- Update install.test.cjs: Hermes install test uses gsd- prefixed paths
- Update runtime-artifact-layout.test.cjs: prefix '' → 'gsd-'

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(#947): restore gsd- prefix on Hermes skills for canonical dispatch

Hermes skills were installing under bare-stem paths
(skills/gsd/<stem>/SKILL.md, name: <stem>) due to prefix: '' set in
ADR-3660 / #3664. This broke /gsd-<stem> dispatch and forced users to
invoke skills without the gsd- namespace prefix.

- src/runtime-artifact-layout.cts: change Hermes skillsKind prefix
  from '' to 'gsd-'; skills now land at skills/gsd/gsd-<stem>/SKILL.md
  with name: gsd-<stem>
- bin/install.js _runLegacyInstallMigrations: invert the #3664
  migration — remove stale bare-stem dirs (using readGsdCommandNames()
  to distinguish GSD-owned stems from user content), keep gsd-* dirs
  which are now canonical
- bin/install.js _runLegacyUninstallCleanup: also remove bare-stem
  dirs on uninstall for clean teardown
- bin/install.js uninstallRuntimeArtifacts: post-cleanup removes
  DESCRIPTION.md and empty skills/gsd/ category dir on Hermes
- bin/install.js: remove skillListPrefix Hermes exception (now uses
  shared 'gsd-' path)
- docs/adr/3660-runtime-artifact-layout-module.md: document #947
  reversal of the bare-stem sub-decision

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* chore: add changeset for #947 fix (#955)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(#947): remove ALL pre-migration bare-stem Hermes skills on reinstall (adversarial review)

Replace readGsdCommandNames()-based bare-stem cleanup (which missed skills
not in the commands source tree, e.g. dev-preferences) with
_removeHermesBareStemDirs(), called AFTER the install loop when the exact
set of installed gsd-<stem>/ dirs is authoritative. For every gsd-<stem>/
written this run, the corresponding bare skills/gsd/<stem>/ is removed.
User-owned bare dirs with no gsd-<stem> counterpart are preserved.

Add two adversarial-review regression tests that FAIL on old code:
- bare skills/gsd/dev-preferences/ removed when gsd-dev-preferences/ installed
- user-owned bare dir with no gsd-<stem> counterpart is preserved (no over-deletion)

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

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/install-nested-layout.test.cjs

@@ -36,7 +36,7 @@ const NEST = [
   // Only the 6 runtimes below keep the nested layout.
   { runtime: 'cline',       scope: 'global', skillsSub: 'skills',     prefix: 'gsd-' },
   { runtime: 'qwen',        scope: 'global', skillsSub: 'skills',     prefix: 'gsd-' },
-  { runtime: 'hermes',      scope: 'global', skillsSub: 'skills/gsd', prefix: ''     },
+  { runtime: 'hermes',      scope: 'global', skillsSub: 'skills/gsd', prefix: 'gsd-' }, // #947: restored canonical prefix
   { runtime: 'augment',     scope: 'global', skillsSub: 'skills',     prefix: 'gsd-' },
   { runtime: 'trae',        scope: 'global', skillsSub: 'skills',     prefix: 'gsd-' },
   { runtime: 'antigravity', scope: 'global', skillsSub: 'skills',     prefix: 'gsd-' },
@@ -127,8 +127,7 @@ for (const { runtime, scope, skillsSub, prefix } of NEST) {
       }
 
       // Total GSD-owned top-level entries must be EXACTLY 6 (only the routers).
-      // For prefix='gsd-' runtimes: count dirs starting with 'gsd-'.
-      // For hermes (prefix=''): count ALL dirs under skills/gsd (everything is GSD-owned).
+      // All nested runtimes (incl. Hermes after #947) use prefix='gsd-'.
       const gsdTopLevelCount = prefix !== ''
         ? topLevel.filter((n) => n.startsWith(prefix)).length
         : topLevel.filter((n) => fs.statSync(path.join(skillsDir, n)).isDirectory()).length;