feat: add versioned memory reassessments

[ezutfen]

Closes #157.

Memory assessments need separate retention and epistemic dimensions. They also need a recovery path after provider failure or changes to the model or recorded evidence. This change adds versioned, append-only assessment history and authorized reassessment jobs.

• Add migration 037 with immutable history, application-role RLS, canonical receipt hashes, and legacy backfill with unknown epistemic state.
• Add idempotent requests, bounded batches, retry status, tenant fairness, and stale-input checks. Completed assessments enqueue durable promotion reevaluation.
• Separate taxonomy, retention, epistemic state, risk, provenance, and calibration. Effective selection requires a pinned contract and matching current evidence.
• Add API, SDK, and MCP interfaces. Preserve legacy fields and the distinction between unknown and zero.

Reassessment, automatic capture, and effective selection default to disabled. The existing promotion policy remains unchanged. Calibration requires an exact, sufficiently sampled profile. The included synthetic dataset verifies metric calculations; it does not establish production calibration.

Validation:

• make check: lint and strict type checks passed; 3,596 tests passed, 2 skipped.
• make compose-ci: root suite 3,564 passed, 34 skipped; SDK 56 passed; hooks 190 passed; MCP 36 passed. This run used a fresh PostgreSQL and pgvector database with the non-owner application role.
• Regression tests cover provider recovery, duplicate requests, concurrent workers, stale content and evidence, authorization, migration reapplication, and calibration artifact replacement.
• Standards and specification reviews have no remaining findings.

See the ADR and completion report for the compatibility mapping, trigger matrix, calibration results, and rollout details.