[codex] Preserve desktop backend log failures

[juliusmarminge]

Keep the backend child log best-effort without discarding why it failed. Setup, record encoding/writes, console mirroring, and size-resynchronization now carry structured operation/path data and exact underlying causes. Only missing log files are treated as an empty initial size; other filesystem failures reach the structured boundary logger.

The rotating writer now propagates failures to that boundary while preserving its size-recovery behavior, including both the original and recovery causes when resynchronization also fails.

Validation:

• vp test apps/desktop/src/app/DesktopBackendOutputLog.test.ts
• vp check
• vp run typecheck

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Note

Low Risk
Observability-only changes in desktop logging; public service API still returns void and falls back to noop on setup failure.

Overview
Desktop backend child output logging stays best-effort (noop on setup failure), but failures are no longer silently dropped. Setup, encode/write, dev console mirroring, and post-write size recovery now emit structured tagged errors with log path, operation, and the exact underlying cause attached for the boundary logger—user-facing messages stay generic and omit low-level diagnostics.

The rotating file writer stops swallowing filesystem errors via ignore / orElseSucceed; only a missing log file is treated as size 0. After a write failure it still resyncs tracked size, then re-fails with the original error, or surfaces a recovery error that carries both causes.

New Vitest coverage asserts setup and write-record failures log DesktopBackendOutputLogSetupError / DesktopBackendOutputLogWriteError with the expected path and cause identity.

^{Reviewed by Cursor Bugbot for commit e87c2f4. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Preserve and log desktop backend output log failures instead of silently ignoring them

• Write failures in DesktopBackendOutputLog are now caught and logged as structured errors (DesktopBackendOutputLogSetupError, DesktopBackendOutputLogWriteError) instead of being silently ignored.
• refreshFileSize now propagates non-NotFound PlatformError instead of defaulting to 0; failed writes attempt a size refresh and may emit DesktopLogFileWriterRecoveryError.
• Console mirroring errors (writeDevelopmentConsoleOutput) are captured and logged as DesktopBackendConsoleWriteError instead of being ignored.
• File operations during pruning and rotation now propagate PlatformError rather than being swallowed.
• Behavioral Change: setup failures now explicitly return Option.none and log a structured error rather than silently falling back to noop.

^{Macroscope summarized e87c2f4.}

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[macroscopeapp]

Approvability

Verdict: Approved

This PR adds structured error handling to desktop backend logging, replacing silent error swallowing with proper error classes and logging. The changes are self-contained observability improvements with comprehensive tests added.

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