fix: surface silent failures across agent, auth, and desktop

[undivisible]

What changed and why

Stops fail-open and silent-failure paths on the current (non-Tauri) desktop/backend stack so errors surface instead of looking healthy.

• Agent VM recovery — GCE/Firestore status recovery no longer discards write or network failures; failed authoritative transitions log and fail closed when they block state.
• Auth custom token — use_custom_token=true returns an error instead of a partial token payload when minting is unimplemented.
• Memories — remove unused recompute_evidence placeholder (no callers).
• Electron — log corrupted Google refresh-token decrypt, non-ENOENT Rewind retention deletes, and primary-screen lookup fallbacks.
• macOS APIClient — log app setup-status check failures instead of empty catch {}.

Product invariants affected

• INV-MEM-1

How it was verified

• cargo check --manifest-path desktop/macos/Backend-Rust/Cargo.toml --bin omi-desktop-backend — passed
• cargo test --manifest-path desktop/macos/Backend-Rust/Cargo.toml --bin omi-desktop-backend agent --offline — passed
• python3 AST parse of backend/database/memories.py — passed
• scripts/pr-preflight — 26 checks passed
• Label: no-changelog-needed (internal logging / reliability only)

Tests

No focused route test exists for the GCE/Firestore recovery path; the existing backend binary agent test passed. Electron changes are log-only on already-handled error paths.

Failure class (fixes)

Failure-Class: none

[github-actions]

Hey @undivisible 👋

Thank you so much for taking the time to contribute to Omi! We truly appreciate you putting in the effort to submit this pull request.

After careful review, we've decided not to merge this particular PR. Please don't take this personally — we genuinely try to merge as many contributions as possible, but sometimes we have to make tough calls based on:

• Project standards — Ensuring consistency across the codebase
• User needs — Making sure changes align with what our users need
• Code best practices — Maintaining code quality and maintainability
• Project direction — Keeping aligned with our product principles and locked invariants

Before your next PR, please skim:

• PRODUCT.md — product north star
• Product invariants — locked rules (shared chat, memory tiers, agent control plane, integrations, brand)

If this was declined for direction or taste, maintainers should cite an invariant ID or open a proposed one — ask if that citation is missing.

Your contribution is still valuable to us, and we'd love to see you contribute again in the future! If you'd like feedback on how to improve this PR or want to discuss alternative approaches, please don't hesitate to reach out.

Thank you for being part of the Omi community!

[undivisible]

Superseded by #10084 after renaming the branch to fix/silent-failure-hardening (GitHub closed this PR when the old head ref was renamed).