Proof output retention: Phase 0/1 follow-up hardening

[tonyketcham]

Summary

Close the residual Phase 0/1 hardening gaps that were explicitly left outside the Phase 1 merge bar.

Source Context

• Cursor cloud-agent follow-up: https://cursor.com/agents/bc-51322132-f3a3-4f80-b0cd-0ed319ccce62
• Implementation PR: docs: plan proof output retention #199
• Proposal artifact: https://github.com/FlatbreadLabs/flatbread/blob/toeknee/proof-output-retention-ce62/docs/proposals/proof-output-retention-plan.md
• Review artifact: https://github.com/FlatbreadLabs/flatbread/blob/toeknee/proof-output-retention-ce62/docs/proposals/proof-output-retention-review.md
• Judge artifact: https://github.com/FlatbreadLabs/flatbread/blob/toeknee/proof-output-retention-ce62/docs/proposals/proof-output-retention-judge.md
• Phase-specific artifact section: https://github.com/FlatbreadLabs/flatbread/blob/toeknee/proof-output-retention-ce62/docs/proposals/proof-output-retention-review.md#L30-L58

Why This Exists

• PR docs: plan proof output retention #199 implements the load-bearing Phase 1 path for task transcripts, but the review keeps several medium/low items open as follow-up rather than merge blockers.
• Phase 0's consumer-inventory appendix did not land, so future edits still need a stable map of TaskState.resultText consumers.
• The review calls out missing end-to-end stitched-prompt coverage, artifact byte-parity coverage, findings-dir parity coverage, noisy resume fallback diagnostics, and source/doc cleanup items.

Acceptance Criteria

• Add or inline a durable consumer inventory for TaskState.resultText and transcript consumers under packages/proof/src/**.
• Replace source-grep tests with behavioral tests where the review calls that out, especially downstream skip on BUDGET-EXCEEDED and resume/transcript consumer wiring.
• Add artifact parity coverage for ${taskId}.md vs ${taskId}.stream.txt modulo the markdown metadata header.
• Add diagnostics for missing registered transcript files after resume, so fallback to bounded resultText is visible to operators and/or downstream prompts.
• Address the low-severity stale comments/docs noted in the review where they are adjacent to the hardening work.

Verification

• pnpm -F @flatbread/proof test
• pnpm verify

Related Phase Issues

• Proof output retention: Phase 0/1 follow-up hardening #200 — Proof output retention: Phase 0/1 follow-up hardening: Proof output retention: Phase 0/1 follow-up hardening #200
• Proof output retention Phase 2: upstream prompt policy and budget preflight #201 — Proof output retention Phase 2: upstream prompt policy and budget preflight: Proof output retention Phase 2: upstream prompt policy and budget preflight #201
• Proof output retention Phase 3: resume, supervisor, and disk ergonomics #202 — Proof output retention Phase 3: resume, supervisor, and disk ergonomics: Proof output retention Phase 3: resume, supervisor, and disk ergonomics #202
• Proof output retention Phase 4: oracle evidence alignment #203 — Proof output retention Phase 4: oracle evidence alignment: Proof output retention Phase 4: oracle evidence alignment #203
• Proof output retention Phase 5: documentation and skill refresh #204 — Proof output retention Phase 5: documentation and skill refresh: Proof output retention Phase 5: documentation and skill refresh #204

Artifact Linkage

This issue is linked back from docs/proposals/proof-output-retention-plan.md and, where relevant, docs/proposals/proof-output-retention-review.md so the repo artifacts and GitHub issues remain navigable in both directions.