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.md

@@ -370,7 +370,7 @@ The `gsd-planner` agent is decomposed into a core agent plus reference modules t
 
 ---
 
-## CLI Modules (102 shipped)
+## CLI Modules (103 shipped)
 
 Full listing: `gsd-core/bin/lib/*.cjs`.
 
@@ -409,6 +409,7 @@ Full listing: `gsd-core/bin/lib/*.cjs`.
 | `frontmatter.cjs` | YAML frontmatter CRUD operations |
 | `gap-checker.cjs` | Post-planning gap analysis (#2493): unified REQUIREMENTS.md + CONTEXT.md decisions vs PLAN.md coverage report (`gsd-tools gap-analysis`) |
 | `graphify.cjs` | Knowledge-graph build/query/status/diff for `/gsd-graphify` |
+| `graphify-command-router.cjs` | ADR-959 capability command router for `gsd-tools graphify` — dispatches build/query/status/diff subcommands; first real capability command cutover (phase 4d-impl-2) |
 | `gsd2-import.cjs` | External-plan ingest for `/gsd-import --from-gsd2` |
 | `init-command-router.cjs` | Thin CJS subcommand router adapter for `gsd-tools init` |
 | `init.cjs` | Compound context loading for each workflow type |