refactor: migrate 40 test files to proper packages

Phase 1: Resolve 5 duplicate pairs (CLI wins 3, SDK wins 1, keep both 1)
Phase 2: Move 9 tests to @agents/core (git, github, hash, uuid, etc.)
Phase 3: Move 27 tests to @agents/sdk (catalog, skill, manifest, etc.)
Phase 4: Move 1 test to @agents/kg (degradation)
Phase 5: Cleanup — delete graph-spike.test.ts

Test distribution now reflects package ownership:
  Core: 203 pass / 1 fail (github timeout)
  SDK:  1082 pass / 0 fail
  KG:   144 pass / 0 fail
  CLI:  606 pass / 0 fail

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: aRustyDev