fix(codex): preserve ambiguous legacy runtime pins

[luvs01]

Motivation

• Legacy persisted codex-runtime.json files created before origin existed are ambiguous because both automatic discovery and doctor --fix-codex-runtime once wrote that shape.
• The previous logic treated absent origin as unpinned and allowed an automatic handover that could silently replace an operator-selected runtime.

Description

• Change provenance semantics so only records with origin: "discovered" are eligible for automatic replacement while ambiguous (origin-less) records are conservatively treated as pinned by default; see src/codex/runtime.ts updates.
• Backfill migration: when a persisted record exactly matches the resolved selection, write it out as origin: "pinned" instead of discovered so legacy operator choices are preserved; implemented in resolveAndPersistCodexRuntime.
• Update tests in tests/codex-integration/codex-runtime.test.ts to assert the conservative handling, and add a short doc note in structure/runtime.md describing the provenance/migration contract.

Testing

• Ran bun run typecheck and it succeeded.
• Ran the focused runtime integration suite with npx -y bun@latest test tests/codex-integration/codex-runtime.test.ts and all tests passed (59 pass, 0 fail).
• Ran npx -y bun@latest run structure:check and npx -y bun@latest run privacy:scan and both succeeded.
• Verified git diff --check; no whitespace or check failures were reported.
• Note: bun test with the environment's bundled Bun (1.2.14) produced an unrelated zlib export error, so the focused test run used npx bun@latest as documented above; bun run test:changed could not run because this checkout lacks a dev comparison ref.

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Codex Task

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[coderabbitai]

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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 2026-09-21T02:38:15.445369Z	45321a2	PR opened

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[github-actions]

✅ Deterministic PR hygiene checks passed.

[devin-ai-integration]

Fixed in 57cc744 — the CodexRuntimePinOrigin doc now describes absent origin as ambiguous legacy state (written by both discovery and doctor --fix-codex-runtime) that is read conservatively as a possible pin, matching persistedCodexRuntimeIsPinned.

[devin-ai-integration]

Fixed in 57cc744 — provenance now follows the command, not observed metadata: while the persisted command stays selected, pinned and origin-less records stay "pinned" even when the binary is upgraded in place or the stored source normalizes to configured. "discovered" is written only when a different command is selected or the prior record was already discovered. Regression tests cover explicit pins and origin-less records across in-place version bumps, plus stored-source normalization.

[devin-ai-integration]

Fixed in 57cc744 — the migrated origin is now derived from whether the persisted command remained selected, independent of source/version changes; structure/runtime.md was updated to state that in-place upgrades and source normalization do not demote a pin, and new tests cover the resolveAndPersist path end to end.