fix: conservative subject-scoped memory assessment

[0YHR0]

Summary

• Stop equating distinct contents in the same Memory Type with semantic contradiction.
• Add optional normalized subject_key for manual notes, governed candidates, and persisted records (additive nullable migration 0057).
• Return UNKNOWN / NO_COMPETING_RECORDS / REVIEW_REQUIRED with reasons and authorized competing IDs. Assess all authorized active candidates before retrieval count/token limits; never infer a winner or confirmed contradiction.
• Preserve subjects during supersession, and retire predecessors atomically when policy-authorized auto-acceptance applies.
• Propagate explicit assessment semantics into model context. Add bilingual Console subject entry and display, docs, lifecycle/API/PostgreSQL regression tests.
• Parallel read-only review identified unbounded competitor metadata; corrected with deterministic IDs capped at 10, exact counts/truncation markers, shared record serialization/budgeting, and non-quadratic assessment allocation.

Validation

• Local full suite: 2242 passed, 304 external-service skips. Independent review/edge verification: 57 targeted tests passed.
• Ruff, JS syntax, diff whitespace passed.
• Live PostgreSQL acceptance passed: separate topics have no competing records; same-topic different contents require review, not a confirmed conflict; approved supersession inherits subject and excludes old version. Temporary synthetic notes cleaned up.
• Five-work-item DeepSeek/MemOS regression completed: 7 dependency transfers, 6 memory retrievals, all 5 model replies ended with stop, primary=final. No confirmed memory conflict was asserted, but a denominator error remains in business output; tracked transparently in Configurable acceptance for coordinated business deliverables #187, not claimed fixed by this PR.

Compatibility: conflict is now nullable; consumers should use conflict_status. Existing notes keep a null subject and historical Run snapshots remain unchanged. No automatic semantic classifier or production memory synchronization is introduced.