[Feature]: Automated test infrastructure (vitest for TS, cargo test for Rust) with CI gating

[matiaspalmac]

Describe the feature

There are no test files anywhere in the repo (no *.test.*, no *.spec.*, no #[cfg(test)] modules). Critical logic has no safety net: tab reducer (open/close/closeOthers/closeToTheRight/closeSaved), git log/stash parsing via \x1f/\x1e separators, autosave, agent prompt aggregator.

Proposed feature:

1. Add vitest to apps/desktop with at least three initial suites: tabs reducer (extract from AppContext), git log/stash parser, agent prompt aggregator.
2. Add Rust tests under #[cfg(test)] mod tests in apps/desktop/src-tauri/src/lib.rs covering validate_branch_name, netstat/lsof parsing fixtures, git_log parser with control bytes, and repo_to_raw_base.
3. Gate CI on pnpm test and cargo test (see related CI issue).

Would you like to implement this feature yourself by sending a PR?

Maybe