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/modes.py

@@ -0,0 +1,99 @@
+"""Conversation modes — how a chat turn is framed and which tools are offered.
+
+A mode bundles three things: a *prompt card* (a system fragment injected each
+turn that tells Lyra how to behave right now), a *tool allow-list* (which of her
+tools she's handed this turn), and — implicitly, via the card — her behavioral
+register.
+
+The problem this solves: one persona + every tool offered every turn made her a
+wishy-washy companion during live poker ("I don't automatically log stack sizes,
+but...") when she should have silently logged and moved on. Modes let the same
+agent be a fast, act-first copilot at the table and her full reflective self
+otherwise — without two personas.
+
+v1 ships two modes:
+  - Talk (default): the companion. Journaling + read-only poker lookups.
+  - Cash: live cash-game copilot. Full live toolset, two-register behavior.
+
+Tournament is deliberately deferred. Strategy-RAG retrieval will later plug into
+Cash's *coaching register* (see the card) without changing this structure.
+"""
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+
+@dataclass(frozen=True)
+class Mode:
+    key: str               # stable id stored on the session row + sent by the UI
+    label: str             # short label for the UI switcher
+    card: str              # system prompt fragment injected per turn ("" = none)
+    tools: tuple[str, ...]  # tool names offered in this mode (must exist in tools.TOOLS)
+
+
+# Read-only poker lookups — safe in any mode, so "how am I running this year?" or
+# "what do we have on Round Mike?" works even when we're just talking.
+_LOOKUPS = ("player_profile", "get_villain_file", "running_stats")
+
+# Always-available core tools (her own agency: journaling/notes).
+_BASE = ("journal_write", "note")
+
+# The full live cash-game toolset.
+_CASH_TOOLS = _BASE + _LOOKUPS + (
+    "start_session", "add_buyin", "log_stack", "log_hand", "record_hand",
+    "add_read", "analyze_spot", "session_stats", "end_session", "generate_recap",
+)
+
+# Talk mode also gets start_session as the *entry point*: opening a session from a
+# normal chat auto-flips the session into Cash mode (see chat.respond).
+_TALK_TOOLS = _BASE + _LOOKUPS + ("start_session",)
+
+
+_CASH_CARD = """You are copiloting Brian's LIVE cash game right now — you're at the table with him, \
+a session is (or should be) open. You move between two registers depending on what he's doing:
+
+• HE HANDS YOU FACTS TO TRACK — his stack, a hand, a read on someone, a rebuy, a result. \
+Log it with the right tool and confirm in ONE short line ("$350 stack logged."). Don't \
+narrate, don't explain what logging is, don't ask permission — just do it. He says his \
+current stack → log_stack. He describes a hand → log_hand (terse) or record_hand (a full \
+hand he wants saved/replayable). A read on a player → add_read. A rebuy → add_buyin. This is \
+the quiet, fast half of the job; he shouldn't feel you working.
+
+• HE ASKS FOR ADVICE, OR TELLS YOU HOW HE'S FEELING — tilted, steaming, card-dead, bored, \
+stuck, "should I have folded the river?" THIS is when he needs you most. Drop the shorthand \
+and be fully present — your real voice, warm and direct and his. Talk him down off tilt, keep \
+him engaged and disciplined through a card-dead stretch, actually walk the strategic spot with \
+him. Strategy and mental game get the real Lyra, not a clipped confirmation. Never clip these.
+
+Stacks and money are in dollars. For ANY equity / who's-ahead / outs / what-a-card-does \
+question, call analyze_spot and report its numbers — never eyeball board math. Keep the \
+session current as the night goes; you can pull session_stats or a player's profile whenever \
+it helps. When he's ready to leave, end_session, and write the recap if he wants it."""
+
+
+TALK = Mode(
+    key="conversation",
+    label="Talk",
+    card="",  # the persona's default voice is the Talk register
+    tools=_TALK_TOOLS,
+)
+
+CASH = Mode(
+    key="poker_cash",
+    label="Cash",
+    card=_CASH_CARD,
+    tools=_CASH_TOOLS,
+)
+
+MODES: dict[str, Mode] = {m.key: m for m in (TALK, CASH)}
+DEFAULT = TALK.key
+
+
+def get(key: str | None) -> Mode:
+    """Resolve a mode key to a Mode, falling back to the default for None/unknown."""
+    return MODES.get(key or "", MODES[DEFAULT])
+
+
+def listing() -> list[dict]:
+    """[{key, label}] for the UI switcher."""
+    return [{"key": m.key, "label": m.label} for m in MODES.values()]