feat: full-fidelity conversation export (chat + tool calls)

Chat only ever lived in SQLite's `exchanges` table (what was *said*); tool
calls were transient — logged to the in-memory ring buffer and gone at
end-of-turn. This adds a persistent record of what Lyra *did* and exports the
two merged into one transcript.

- memory: new `tool_events` table + `add_tool_event`/`tool_events` accessors;
  `delete_session` cascades to it.
- chat: persist each tool call (name/args/result) right where it fires, in both
  the non-stream and stream paths. Move the user `remember` to just after
  assembly so its timestamp precedes mid-turn tool events — keeps the export in
  true chronological order (and records when the message actually arrived).
- transcript: new module renders a session as Markdown (Brian/Lyra speech with
  ⚙ tool-call lines interleaved) or JSON (machine-readable event stream).
- server: GET /sessions/{id}/export?format=md|json (attachment download).
- ui: ⬇ Export button by the session selector (Markdown or JSON).

Doubles as the receipt for "did the tool actually fire?" — the thing that was
invisible when she'd reply about a hand without logging it.

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

lyra/transcript.py

@@ -0,0 +1,77 @@
+"""Full-fidelity conversation export: interleave what was *said* (chat exchanges)
+with what Lyra *did* (tool calls) in chronological order.
+
+The chat only ever lives in SQLite (`exchanges` + `tool_events`); this is the one
+place that renders a whole session back out as a portable artifact — Markdown for
+reading / pasting into RTO or another model, JSON for machine reprocessing.
+"""
+from __future__ import annotations
+
+import json
+
+from lyra import clock, memory
+
+# How roles/actions are labeled in the Markdown transcript.
+_SPEAKER = {"user": "Brian", "assistant": "Lyra"}
+
+
+def _merged(session_id: str) -> list[dict]:
+    """Speech + actions for a session, merged oldest-first by wall-clock time."""
+    events: list[dict] = []
+    for e in memory.history(session_id):
+        events.append({"type": "message", "role": e.role, "content": e.content,
+                       "ts": e.created_at})
+    for t in memory.tool_events(session_id):
+        events.append({"type": "tool", "tool": t["tool"], "args": t["args"],
+                       "result": t["result"], "ts": t["created_at"]})
+    # created_at is an ISO string; lexicographic sort == chronological sort.
+    events.sort(key=lambda ev: ev["ts"])
+    return events
+
+
+def _fmt_args(args) -> str:
+    """Compact one-line rendering of a tool call's arguments."""
+    if isinstance(args, dict):
+        return ", ".join(f"{k}={json.dumps(v, default=str)}" for k, v in args.items())
+    return "" if args is None else str(args)
+
+
+def as_markdown(session_id: str, name: str | None = None) -> str:
+    events = _merged(session_id)
+    title = name or session_id
+    lines = [f"# Conversation — {title}",
+             f"_Exported {clock.stamp()} · session `{session_id}` · "
+             f"{len(events)} events_", ""]
+    for ev in events:
+        stamp = clock.short(ev["ts"])
+        if ev["type"] == "message":
+            who = _SPEAKER.get(ev["role"], ev["role"].capitalize())
+            lines.append(f"**{who}** · {stamp}")
+            lines.append((ev["content"] or "").rstrip())
+            lines.append("")
+        else:
+            result = (ev["result"] or "").strip().replace("\n", " ")
+            if len(result) > 200:
+                result = result[:197] + "…"
+            lines.append(f"  ⚙ `{ev['tool']}({_fmt_args(ev['args'])})` → {result}")
+            lines.append("")
+    return "\n".join(lines).rstrip() + "\n"
+
+
+def as_json(session_id: str, name: str | None = None) -> dict:
+    return {
+        "session_id": session_id,
+        "name": name,
+        "exported_at": clock.stamp(),
+        "events": _merged(session_id),
+    }
+
+
+def build(session_id: str, fmt: str = "md", name: str | None = None):
+    """Return (content_str, media_type, filename) for the requested format."""
+    safe = "".join(c if c.isalnum() or c in "-_" else "_" for c in session_id)[:60]
+    if fmt == "json":
+        body = json.dumps(as_json(session_id, name), indent=2, ensure_ascii=False)
+        return body, "application/json", f"lyra_{safe}.json"
+    body = as_markdown(session_id, name)
+    return body, "text/markdown; charset=utf-8", f"lyra_{safe}.md"