`hermes -c`/`--resume` (continue last session) resolved the globally
most-recently-used session, then cd'd into *its* recorded cwd. So running
`hermes -c` from repo A could land you in repo B's session — the session
you last touched anywhere, not the last one *here*.
Now `_resolve_last_session` scopes to the current workspace first: the git
repo root when CWD is inside a repo (so all sessions across its
subdirs/worktrees group together), else the CWD itself — matching the
`workspace_key` identity `hermes sessions list --workspace` already groups
on. It falls back to the unscoped global MRU when no session matches the
current workspace, preserving the old behaviour for fresh directories.
Adds `workspace_key` param to `SessionDB.search_sessions` and a
`_workspace_key_clause` SQL helper that mirrors `workspace_key()`: a row
matches when its `git_repo_root` equals the key, or (legacy rows without
git metadata) when its `cwd` is at or under it.
- use a grouped last_active join in search_sessions to avoid per-row correlated max lookups
- always close SessionDB in _resolve_last_session via finally and add regression coverage for search failure cleanup
- order session listing by computed last_active in SessionDB so callers get MRU rows directly
- keep _resolve_last_session as a single-row lookup and add regression coverage for >20 session sampling
