Fix workspace restore/connect idempotency and strict RPC parsing

[jmcte]

Summary

This issue captures fixes for workspace lifecycle and API robustness in CodexMonitor.

Scope

• Fix workspace restore hook so a failed connect/list cycle does not permanently mark workspace as restored.
• Make local workspace connect idempotent and safe under repeated calls.
• Make optional RPC parsing strict for u32 and string-array inputs.
• Centralize Tauri invoke fallback/err handling in service wrappers (not just listWorkspaces).

Acceptance

• A failed restore attempt is retried instead of being skipped.
• Repeated local connect calls do not spawn multiple sessions.
• Invalid optional inputs for optional RPC numeric/array fields return explicit errors.
• Non-Tauri environments use safe fallbacks/errors consistently across service methods.
• Added regression tests for each behavior.

Work items

1. useWorkspaceRestore marker lifecycle

• move restored marker to after successful restore flow

2. connect_workspace_core

• make connect operation idempotent + race-safe

3. rpc parser helpers

• parse_optional_u32 and parse_optional_string_array currently return None on malformed values
• change to Result<Option<_>, String> and propagate parse errors from callers

4. Tauri service wrappers

• add shared invoke wrappers in src/services/tauri.ts
• keep listWorkspaces returning [] when bridge is missing
• return actionable errors for other commands when bridge is missing

5. Tests

• add/extend frontend hook tests + daemon parse/connect tests
• run targeted test suites and typecheck