fix(cursor): retain adjacent mid-stream echo diagnostics

[luvs01]

Motivation

• The mid-stream echo observer used a single pending corruptionWatch which could be overwritten by a later marker inside the 512-character corruption window, losing earlier findings and their accumulated corruption evidence.

Description

• Replace the single corruptionWatch with a bounded array corruptionWatches to track multiple concurrent pending watches and preserve up to MAX_MIDSTREAM_FINDINGS findings. (edited src/adapters/cursor/envelope-echo.ts).
• Apply incoming text to every active corruption watch and settle any watches whose window has been filled, pushing their boolean corruption result into recorded and removing the settled watch. (edited src/adapters/cursor/envelope-echo.ts).
• Adjust the findings() path to flush all remaining pending watches before returning recorded findings. (edited src/adapters/cursor/envelope-echo.ts).
• Update and add regression tests that assert closely spaced markers both survive and retain correct offsets and corruption flags. (edited tests/cursor-envelope-echo-retry.test.ts).

Testing

• ✅ Ran the focused suite bun test tests/cursor-envelope-echo-retry.test.ts, and the updated tests passed.
• ✅ Ran bun run typecheck which completed successfully.
• ✅ Ran bun run privacy:scan which completed successfully.
• ⚠️ Ran the full repository test run (bun run test) but it encountered numerous unrelated timeouts and shared-state failures outside the modified Cursor observer code; those failures are existing, unrelated CI-scale issues and were not caused by this focused change.

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Codex Task

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[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-08-31T00:49:48.828041Z	87b2ab0	PR opened

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[github-actions]

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[coderabbitai]

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[github-actions]

✅ READY

• all PR quality gates passed.

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✅ Deterministic PR hygiene checks passed.

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.

[luvs01]

Closing: superseded by combined PR #610, which carries this PR's adjacent mid-stream echo diagnostics retention together with the bounded reasoning-quarantine change on current dev. Combined tests: 47 + 54 pass.