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/web/static/style.css

@@ -99,6 +99,29 @@ body {
   border-top: 1px solid var(--border);
 }
 
+/* Mode badge: the always-visible Talk/Cash toggle. Hidden on desktop (the header
+   <select> handles it there); shown in the minimal mobile header (see media query). */
+.mode-badge {
+  display: none;
+  align-items: center;
+  gap: 4px;
+  font-family: var(--font-console);
+  font-size: 0.82rem;
+  color: var(--text-fade);
+  background: var(--bg-line);
+  border: 1px solid var(--border);
+  border-radius: 999px;
+  padding: 4px 11px;
+  -webkit-tap-highlight-color: transparent;
+}
+/* Cash mode: light up the badge (and the chat brand) so the table state is obvious. */
+body.cash-mode .mode-badge {
+  color: var(--accent);
+  border-color: var(--accent);
+  background: var(--accent-soft);
+}
+body.cash-mode .brand { color: var(--accent); }
+
 label, select, button {
   font-family: var(--font-console);
   font-size: 0.9rem;
@@ -822,10 +845,11 @@ select:hover {
     gap: 12px;
   }
 
-  /* Mobile header is [≡]  Lyra  …  [●] — hide everything else. */
-  #model-select > *:not(.hamburger-menu):not(.brand):not(.brand-dot) {
+  /* Mobile header is [≡]  Lyra  [♠ Cash]  [●] — hide everything else. */
+  #model-select > *:not(.hamburger-menu):not(.brand):not(.brand-dot):not(.mode-badge) {
     display: none;
   }
+  .mode-badge { display: inline-flex; margin-left: 4px; }
   .brand {
     display: block;
     font-family: var(--font-console);