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>

tests/capability-command-dispatch.test.cjs

@@ -741,16 +741,22 @@ describe('dispatchCapabilityCommand — async router returns a Promise → struc
   });
 });
 
-// ─── 9. Behavior-preservation: real registry has empty commandFamilies ────────
+// ─── 9. Behavior-preservation: real registry commandFamilies ────────────────
 
 describe('dispatchCapabilityCommand — real registry behavior-preservation', () => {
-  test('real capability-registry.cjs commandFamilies is {} (no capability declares commands)', () => {
+  test('real capability-registry.cjs commandFamilies is exported and is an object', () => {
+    // Phase 4d-impl-2: graphify was the first capability to declare a command family.
+    // This test was originally written as "commandFamilies must be empty today" but
+    // now asserts the structural contract instead (exported, object) since the graphify
+    // cutover populates it.
     const realRegistry = require('../gsd-core/bin/lib/capability-registry.cjs');
     assert.ok(realRegistry.commandFamilies, 'commandFamilies must be exported');
-    assert.deepEqual(
-      Object.keys(realRegistry.commandFamilies),
-      [],
-      'real registry commandFamilies must be empty today',
+    assert.strictEqual(typeof realRegistry.commandFamilies, 'object',
+      'commandFamilies must be an object');
+    // graphify is the first (and currently only) real capability command family
+    assert.ok(
+      Object.prototype.hasOwnProperty.call(realRegistry.commandFamilies, 'graphify'),
+      'real registry commandFamilies must include graphify after 4d-impl-2 cutover',
     );
   });