feat: undo / delete logged entries (fix fat-fingered live logging)

Previously the only delete was whole-session, so a mis-logged stack or a
mis-parsed hand was stuck on the HUD. Now:

- undo_last tool ("scratch that") — deletes the most recent hand/stack/read/
  scar/confidence/reset in the live session; added to the Cash toolset.
- poker.delete_hand/stack/read/ritual + delete_entry dispatch + undo_last.
- DELETE /session/entry/{kind}/{id} endpoint.
- HUD: per-row × delete buttons on hands, confidence-bank, and scar-note rows
  (stack/read deletes via the tool). Row ids now surfaced in the hud() bundle.
- test_modes.py +2 (undo_last across kinds, tool handler); 46 green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lyra/modes.py

@@ -44,6 +44,7 @@ _CASH_TOOLS = _BASE + _LOOKUPS + (
     "start_session", "add_buyin", "log_stack", "log_hand", "record_hand",
     "add_read", "analyze_spot", "session_stats", "session_state", "end_session",
     "generate_recap", "scar_note", "confidence_bank", "alligator_blood", "reset_ritual",
+    "undo_last",
 )
 
 # Talk mode also gets start_session as the *entry point*: opening a session from a