feat: expose durable feedback history

[kachofugetsu09]

Summary

• expose immutable accepted feedback through the ordinary proactive-feedback.history.v1 composition service
• replace the old Observe/outbox writer path with stable read-only cursor pages
• keep legacy inbox/outbox rows and tables intact while new accepted facts append without update or delete
• validate exact legacy/current SQLite lineage, integrity, finite values, and canonical payload hashes

Verification

• 32 Python tests passed
• 6 Node tests passed
• Pyright: 0 errors
• compileall and exact plugin API v3 contract passed
• Terra xhigh semantic gate: APPROVE at 531eae4e4ac4714aad5417b8257a724007728345

State and rollback

• formal workspace and runtime were not changed
• legacy feedback, inbox, outbox, and published-cursor rows are retained in full
• rollback by closing this draft PR and returning consumers to the current main commit