EPIC-0460: recover transient V2 publication reads

[epowell40]

Summary

• retry bounded read-only V2 session-index and exact-publication fetches
• preserve strict shared schema validation after transport recovery
• add Candidate 7 failure-family regression without replaying Assignment or Revit work
• regenerate artifact-bound certification evidence

Validation

• npm run build
• node --test --import tsx test/assignment_kernel_v2_session_index_contract.test.ts
• npm run check:tool-certification-evidence
• npm test: 2889 tests, 2886 passed, 3 skipped, 0 failed
• git diff --check