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/ARCHITECTURE.md

@@ -375,6 +375,7 @@ Node.js CLI utility (`gsd-tools.cjs`) with domain modules split across `gsd-core
 | `capability-registry.cjs`  | Generated central Capability Registry — role-partitioned index of all co-located capability declarations; emitted by `scripts/gen-capability-registry.cjs` (ADR-894 §5) |
 | `loop-resolver.cjs`        | Loop Extension Point resolver — ADR-857 phase 3c registry-consuming query; filters `byLoopPoint` by config activation, renders active hooks as markdown, emits `{ point, activeHooks, rendered }` envelope; `gsd-tools loop render-hooks <point>` |
 | `capability-state.cjs`     | Unified capability-state resolver — ADR-857 phase 4b; composes install profile, runtime surface, and config activation into one per-capability view; pure `resolveCapabilityState` + I/O `cmdCapabilityState`; `gsd-tools capability state [--config-dir <path>]` |
+| `graphify-command-router.cjs` | ADR-959 capability command router — first real capability command cutover (phase 4d-impl-2); extracted from the `case 'graphify':` arm in `gsd-tools.cjs`; dispatches build/query/status/diff subcommands; discovered via `commandFamilies` in the capability registry |
 
 
 ---