SessionInfo already carries git_branch from the backend, but neither the
ctrl-k command palette nor the sidebar search function included it in
their matching fields. Typing a branch name matched nothing.
- session-search.ts: add session.git_branch to sessionMatchesSearch
- command-palette/index.tsx: thread git_branch through SessionEntry and
into the keywords array for both sessions and archived sessions groups
- session-search.test.ts: cover full, partial, and "main" branch matches
ethernet
4e7b0389ea