feat(registry): component_hash_id — stable id system for workflow references

Problem: canonical_id is readable but mutable; if a component is renamed,
all workflows referencing it by canonical_id break.

Solution: dual-id system
- component_hash_id: cmp_{sha256(canonical_id).slice(0,8)}, derived deterministically,
  never changes, safe for workflow references
- canonical_id: human-readable name, used for search and display
- idx:{canonical_id} KV key: reverse-lookup index for resolving canonical_id → hash_id

Changes:
- types.ts: SandboxResult.component_id → component_hash_id + canonical_id,
  added 'data' to category enum
- submitComponent.ts: deriveHashId(), writes idx: reverse-lookup on submit
- queryComponents.ts: full rewrite — removed KBDB dependency, uses SUBMISSIONS_KV;
  supports both cmp_* and canonical_id as query id; Phase 0 keyword search
  with note to upgrade to Vectorize in Phase 2
- sandboxAcceptance.ts: updated field names, fixed TextDecoder TS type
- ensureTemplate.ts: removed KBDB dependency, now a KV health check
- tests: updated component_id → canonical_id
- CONTRIBUTING.md: explain hash_id derivation and dual-id workflow reference syntax

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

registry/tests/sandboxAcceptance.test.ts

@@ -40,7 +40,7 @@ describe('runSandboxAcceptance', () => {
     const wasm = makeMinimalWasm(10);
     const result = runSandboxAcceptance(wasm, BASE_CONTRACT);
     expect(result.success).toBe(true);
-    expect(result.component_id).toBe('validate_json');
+    expect(result.canonical_id).toBe('validate_json');
     expect(result.version).toBe('v1');
   });
 
@@ -53,7 +53,7 @@ describe('runSandboxAcceptance', () => {
     expect(result.failed_step).toBe('size_check');
     expect(result.reason).toContain('超過上限');
     expect(result.guide_anchor).toBeDefined();
-    expect(result.component_id).toBe('validate_json');
+    expect(result.canonical_id).toBe('validate_json');
     expect(result.version).toBe('v1');
   });