hygiene(#268): pr-preservation drain-log for #434 (memory-reconciliation CC schema)

[AceHack]

Summary

Otto-268 backfill: drain-log for PR #434 (drain follow-up #2 for #226 — memory-reconciliation algorithm CC schema alignment), covering 3 substantive design-correctness findings.

Per Otto-250 (PR review comments + responses + resolutions are high-quality training signals).

Coverage — all FIX outcomes (Copilot only on this PR)

• P1 idempotency strategy: design said "appends" but didn't specify how repeated runs avoid re-appending the same conflict (unbounded growth risk) — fixed via explicit canonical-key → CC-NNN mapping with in-place-update vs delimited-subsection alternatives.
• P1 Open-table targeting: "appending rows" ambiguous given three tables (Open / Resolved / Stale) — fixed by specifying writes target the Open table (or a delimited autogenerated subsection within Open).
• P2 placeholder-vs-column-header mismatch: design example used "Parties:" / "Resolution:" but live schema headers are "Between" / "Resolution-so-far" — fixed via rename matching live grep output.

Pattern observations

1. Design-doc placeholders should match live-schema column names — verify-via-grep + rename is the cheap fix; expensive fix comes after implementation breaks.
2. Idempotency requirements need explicit canonical-key strategies — generalizes to any append-only-with-deduplication schema-driven generator.
3. Three-table schema awareness (Open / Resolved / Stale) vs single-table append — be explicit about which sub-table is generator's write scope.
4. Per-PR reviewer-coverage signal: Copilot-only here (design-spec text); Codex tends to fire on shell scripts, math docs, security threat models.

Test plan

• All 3 thread IDs preserved verbatim with severity + outcome.
• Drain-log shape matches existing docs/pr-preservation/*-drain-log.md template.

🤖 Generated with Claude Code

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[Copilot]

Pull request overview

Adds a PR-preservation “drain log” for PR #434, capturing the Copilot review threads and their FIX resolutions so the repo keeps an auditable, training-signal-grade record of design-spec corrections around CC schema alignment and generator idempotency.

Changes:

• Added docs/pr-preservation/434-drain-log.md documenting 3 Copilot threads (P1/P1/P2) and the applied fixes.
• Recorded the resolved design decisions: Open-table write scope, canonical-key→CC-NNN idempotency strategy, and placeholder/header alignment with docs/CONTRIBUTOR-CONFLICTS.md.