fix(spend): classify synced state paths with POSIX rules on every host

[lidge-jun]

Summary

Fixes the dev Cross-platform CI failure in windows 5/9 (run 36891940246 on dev 8a3a7762fe). Five cases in tests/lib/synced-state-location.test.ts from #6398 received undefined where they expected icloud-drive, file-provider or icloud-desktop-documents.

The detector classifies macOS paths only and returns early unless the platform is darwin. The tests inject platform: "darwin" with POSIX fixtures, so on a Windows host the detection ran, but it built and resolved paths with the host's node:path. That produced \\ separators and drive-letter prefixes that never matched the fixture paths. The module now uses node:path's posix implementation. On macOS, the only platform where detection runs, posix is the native implementation, so runtime behavior is unchanged. On Windows and Linux the function still returns before touching any path.

A new case checks that every path the detector probes stays in POSIX form, with no backslash, even when the host is Windows.

Verification

• I did not run local test suites or typecheck, on the project owner's explicit instruction. Hosted CI at the exact head is the evidence. The PR-lane Cross-platform CI skips the Windows test shards, so the Windows fix will be shown by the next full dev Cross-platform CI run, not by this PR's checks.
• Static checks run locally: git diff --check, bun run scripts/privacy-scan.ts and bun run structure:check pass.

Checklist

• Scope stays focused and avoids unrelated cleanup.
• Docs or release notes were updated when needed. No user-facing change.
• Security-sensitive changes were reviewed for secrets, auth, and unsafe defaults. This is a path-module swap in an advisory, read-only detector, with no security boundary.

Summary by CodeRabbit

• Bug Fixes
  • Improved detection of synced-state locations for macOS paths, including paths under Documents. Classification now uses consistent slash-based paths even when running on another operating system.

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-01T16:41:48.730965Z	4dfc950	PR opened

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 06cc381 and 4dfc950.

📒 Files selected for processing (2)

• src/lib/synced-state-location.ts
• tests/lib/synced-state-location.test.ts

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📝 Walkthrough

Walkthrough

The synced state location module now uses POSIX path operations on every host. A test checks that a Darwin probe classifies a Documents path as icloud-desktop-documents and that paths passed to entryExists use the expected home-directory prefix without backslashes.

Changes

Synced state path handling

Layer / File(s)	Summary
POSIX path behavior src/lib/synced-state-location.ts, tests/lib/synced-state-location.test.ts	The module uses posix.join and posix.resolve. The test verifies macOS path classification and the paths passed to entryExists.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to 4dfc9

No actionable production issue is established in this change. POSIX path classification remains limited to macOS, so the change is ready to merge subject to normal checks.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: using POSIX path rules on every host to fix synced-state path classification.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✅ Deterministic PR hygiene checks passed.

[lidge-jun]

Maintainer integration record (MAINTAINERS.md, dev-only)

• Maintainer PR fix(spend): classify synced state paths with POSIX rules on every host #6414. It fixes the dev Cross-platform CI windows 5/9 failure from fix(spend): name the refused ledger file and condition, warn on synced state directories #6398's new tests (run 36891940246, dev 8a3a7762fe). Exact head 4dfc9503cb75f362195c412903459131b2187d48, base 06cc3815c0.
• Root cause: src/lib/synced-state-location.ts used the host node:path, so on Windows the darwin-injected fixtures were joined and resolved with backslashes and drive letters. The fix is to use posix path ops. Runtime behavior on macOS is unchanged, and other platforms still return early. A new case asserts that the probed paths stay POSIX.
• Hosted CI at the head: Cross-platform CI 36893662340 succeeded, as did React Doctor 36893662324 and PR hygiene 36893844786. The PR lane skips the Windows test shards, so only the next full dev Cross-platform run can prove the Windows fix. enforce-target runs 36893662370 and 36893844656 were still queued for a runner at report time.
• Local suites: not run, on explicit owner instruction.
• Security: no boundary involved. This is a path-module swap in an advisory, read-only detector.