feat: session modes (Talk/Cash) + live session HUD

Lyra now switches register based on what she's doing at the table instead of
being a wishy-washy companion mid-session.

Modes (lyra/modes.py):
- Talk (default companion) + Cash (live cash copilot); a mode = prompt card +
  tool allow-list. Tool gating via tools.specs(allow=).
- Two-register Cash voice: act-first one-line logging when fed facts; full warm
  companion voice for strategy / tilt / mental game.
- mode persisted per chat session (new sessions.mode column); auto-switch into
  Cash when start_session fires; UI forces cloud backend in Cash (tools only
  fire there).

Stack tracking + HUD:
- log_stack tool + poker_stack_log table; live net while sitting (stack - buy-in).
- poker.hud() bundle; /session HUD page (stack sparkline, hands, villains, notes,
  stats) polling /session/data every 5s; Talk/Cash switcher + Session nav.

Endpoints: /session, /session/data, GET/POST /sessions/{id}/mode, /modes.
tests/test_modes.py (gating, mode roundtrip, stack/HUD); 36 tests green. v0.3.0.

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

lyra/memory.py

@@ -32,6 +32,7 @@ CREATE INDEX IF NOT EXISTS idx_session_created ON exchanges(session_id, created_
 CREATE TABLE IF NOT EXISTS sessions (
     id TEXT PRIMARY KEY,
     name TEXT,
+    mode TEXT,            -- conversation mode (see lyra/modes.py); NULL = default
     created_at TEXT NOT NULL
 );
 
@@ -131,6 +132,12 @@ def _connection() -> sqlite3.Connection:
         _conn.execute("PRAGMA busy_timeout=5000")
         _conn.execute("PRAGMA journal_mode=WAL")
         _conn.executescript(SCHEMA)
+        # Migrations for DBs created before a column existed (no-op if present).
+        for ddl in ("ALTER TABLE sessions ADD COLUMN mode TEXT",):
+            try:
+                _conn.execute(ddl)
+            except sqlite3.OperationalError:
+                pass
         _conn_path = cfg.db_path
     return _conn
 
@@ -236,6 +243,21 @@ def ensure_session(session_id: str, name: str | None = None) -> None:
             conn.execute("UPDATE sessions SET name = ? WHERE id = ?", (name, session_id))
 
 
+def get_session_mode(session_id: str) -> str | None:
+    """The session's conversation mode key, or None if unset (caller applies default)."""
+    conn = _connection()
+    r = conn.execute("SELECT mode FROM sessions WHERE id = ?", (session_id,)).fetchone()
+    return r["mode"] if r and r["mode"] else None
+
+
+def set_session_mode(session_id: str, mode: str) -> None:
+    """Persist the session's conversation mode (creating the session row if needed)."""
+    ensure_session(session_id)
+    conn = _connection()
+    with conn:
+        conn.execute("UPDATE sessions SET mode = ? WHERE id = ?", (mode, session_id))
+
+
 def list_sessions() -> list[dict]:
     """All known sessions (named rows + any session that has exchanges), newest first."""
     conn = _connection()