feat(#972): graphify command cutover — first capability owning a command family (ADR-857 phase 4d-impl-2) (#975)

Migrate graphify into a Capability that owns its `graphify` command family,
dispatched via the registry (#961 mechanism) instead of a hardcoded case.
graphify is now an enable/disable plug-in.

- src/graphify-command-router.cts: routeGraphifyCommand (standard route*Command),
  reproduces the removed case EXACTLY (query +--budget, status, diff, build,
  hidden build snapshot, usage/unknown errors); injectable _graphify test seam.
- capabilities/graphify/capability.json: role feature, tier:full, skills:[graphify],
  config:{graphify.enabled default false}, commands:[{family:graphify, module,
  router:routeGraphifyCommand}].
- removed case 'graphify' from gsd-tools.cjs; graphify now flows
  default -> dispatchCapabilityCommand -> commandFamilies.graphify -> router.
- regenerated registry (commandFamilies/bySkill/configSchema/profileMembership/
  capabilityClusters for graphify); tier:full keeps 4c install/surface a no-op.

Equivalence-proven: 8 recording-mock unit tests assert the exact fn+args per
subcommand (budget, snapshot-vs-build); 9 subprocess tests assert distinguishing
output shapes; existing graphify tests pass unchanged through the new path.

Surfaced (not silently accepted): the pre-existing --budget-no-value NaN no-op
quirk, preserved for equivalence, filed separately.

Closes #972

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

docs/INVENTORY-MANIFEST.json

@@ -1,5 +1,5 @@
 {
-  "generated": "2026-06-09",
+  "generated": "2026-06-10",
   "families": {
     "agents": [
       "gsd-advisor-researcher",
@@ -297,6 +297,7 @@
       "federated-config.cjs",
       "frontmatter.cjs",
       "gap-checker.cjs",
+      "graphify-command-router.cjs",
       "graphify.cjs",
       "gsd2-import.cjs",
       "init-command-router.cjs",