fix(artifacts): fail open when optional stats cannot be written

[hxy91819]

Summary

• make recordStats metadata writes best effort
• preserve raw output and child exit codes when the artifact directory is unavailable
• keep explicit --store failures strict
• apply the same fail-open behavior to Codex immediate skip stats

Root cause

Optional telemetry used the same strict metadata writer as explicit artifact storage. An EROFS or ENOTDIR error therefore replaced an already completed command result, including explicit raw output.

Tests

• env -u TOKENJUICE_NO_OMISSION pnpm exec vitest run test/core/wrap.test.ts -t "preserves raw output when optional stats cannot be written|keeps explicit artifact storage failures strict"
• env -u TOKENJUICE_NO_OMISSION pnpm exec vitest run test/hosts/codex.test.ts -t "keeps raw bypasses fail-open when optional stats cannot be written"
• pnpm lint
• pnpm typecheck
• packaged CLI probe with TOKENJUICE_ARTIFACT_DIR pointing at an existing file: raw marker and exit 7 preserved

Impact

No documentation, packaging, or release behavior changes. Explicit storage remains strict.

[chatgpt-codex-connector]

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