[codex] Structure desktop backend settings read errors

[juliusmarminge]

Summary

• replace the exists/read fallback pair with one race-free read
• treat only NotFound as an expected missing settings file
• log other read failures as a structured Schema error with the settings path and exact platform cause while preserving the existing defaults fallback

Verification

• vp test apps/desktop/src/backend/DesktopBackendConfiguration.test.ts (5 passed)
• vp check (passes; 20 existing warnings)
• vp run typecheck

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Note

Low Risk
Localized desktop bootstrap config read path; behavior on missing files is unchanged and failures still degrade to defaults with better observability.

Overview
Desktop backend config now loads persisted OTLP settings with a single readFileString instead of exists plus read, avoiding a race when the file appears or disappears between checks.

Missing settings are handled only when the read fails with NotFound; other filesystem errors (e.g. permission denied) emit a structured DesktopBackendObservabilitySettingsReadError via Effect.logWarning with component, settingsPath, and the platform cause, then still fall back to empty observability defaults so startup is unchanged.

A new test asserts that behavior on read failure: bootstrap URLs stay undefined and the logged error matches the path and cause.

^{Reviewed by Cursor Bugbot for commit fc020f5. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Structure desktop backend observability settings read errors with DesktopBackendObservabilitySettingsReadError

• Adds a new DesktopBackendObservabilitySettingsReadError Schema tagged error class in DesktopBackendConfiguration.ts with settingsPath and cause fields, replacing the previous generic string warning log.
• When reading persisted observability settings fails, non-NotFound errors (e.g. PermissionDenied) now log a structured warning annotated with component: desktop-backend-configuration; NotFound errors return empty settings silently.
• Removes the FileSystem.exists pre-check, instead attempting readFileString directly and branching on the error reason tag.
• Adds a test in DesktopBackendConfiguration.test.ts that injects a failing FileSystem layer and asserts the structured error is logged with the expected fields.

^{Macroscope summarized fc020f5.}

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[macroscopeapp]

Approvability

Verdict: Approved

Refactors error handling to use structured error classes with better context for debugging. Runtime behavior is preserved - read failures still gracefully return empty settings. Original file author with comprehensive test coverage.

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