feat(training): Style Studio — upload, rich corpus, lessons, curator portrait, chat

Six-phase upgrade of /training from a read-only dashboard into a full
Style Studio for managing Daphna's style corpus.

- Upload Sheet on /training: file → proofread preview → commit (no more
  CLI-only `upload-training` skill).
- Rich corpus metadata: GET /api/training/corpus returns summary, outcome,
  key_principles, page_count, parties (regex), legal_citation, lessons_count.
  PATCH endpoint for chair edits. CorpusDetailDrawer with 4 tabs (details
  /content/lessons/patterns) replaces the bare table row.
- LLM metadata enrichment: style_metadata_extractor + MCP tools
  (style_corpus_enrich, style_corpus_pending_enrichment) fill summary
  /outcome/key_principles via claude_session (free, host-side).
- Per-decision lessons: new decision_lessons table + 4 REST endpoints +
  LessonsTab in drawer; hermes-curator now auto-posts findings as
  decision_lessons(source=curator).
- Curator Portrait tab: prompt rendered with link to Gitea, recent
  curator findings, style_analyzer training prompts, propose-change
  form that writes proposals to data/curator-proposals/ for manual
  chair review (no auto-mutation of the agent file).
- Style chat tab: SSE-streamed conversations with the style agent.
  New host-side pm2 service (legal-chat-service, port 8770) wraps
  claude CLI with stream-json + --resume continuation; FastAPI proxies
  via host.docker.internal. Zero API cost — uses chaim's claude.ai
  subscription. chat_conversations + chat_messages persist history.

Architecture: keeps the existing rule that claude_session only runs
on the host (not the container). The new legal-chat-service is the
canonical bridge between the container and the local CLI for the chat
feature; everything else (upload, metadata, lessons) stays within the
container's existing capabilities.

Audit script (scripts/audit_training_corpus.py) included for verifying
which corpus rows still need enrichment.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

mcp-server/src/legal_mcp/chat_service/server.py

@@ -0,0 +1,144 @@
+"""HTTP+SSE bridge from FastAPI (in container) to local claude CLI.
+
+Endpoints:
+    POST /chat/start    — body: {prompt, system?, resume_session_id?}
+                          returns SSE stream of events from
+                          ``claude_session.query_streaming``.
+    GET  /health        — liveness probe.
+
+Run with pm2:
+    pm2 start ecosystem.config.cjs --only legal-chat-service
+
+Standalone for dev:
+    cd ~/legal-ai/mcp-server
+    .venv/bin/python -m legal_mcp.chat_service.server --port 8770
+
+We intentionally bind to 127.0.0.1 only — the FastAPI container reaches
+us via ``host.docker.internal``, and exposing the bridge publicly would
+let anyone run claude CLI commands against Daphna's session.
+"""
+
+from __future__ import annotations
+
+import argparse
+import asyncio
+import json
+import logging
+import os
+import sys
+from typing import Any
+
+from aiohttp import web
+
+# Run-via-CLI bootstrap so ``python -m legal_mcp.chat_service.server``
+# works even when the package isn't installed (it is in the venv, but
+# this safeguard keeps the entrypoint robust).
+_pkg_root = os.path.dirname(os.path.dirname(os.path.dirname(__file__)))
+if _pkg_root not in sys.path:
+    sys.path.insert(0, _pkg_root)
+
+from legal_mcp.services import claude_session  # noqa: E402
+
+logger = logging.getLogger("legal_chat_service")
+
+
+async def health(request: web.Request) -> web.Response:
+    return web.json_response({"ok": True, "service": "legal-chat-service"})
+
+
+async def chat_start(request: web.Request) -> web.StreamResponse:
+    """Drive ``claude_session.query_streaming`` and forward events as SSE.
+
+    Request body (JSON):
+        prompt: str                    — required, user message
+        system: str | None             — system instructions (ignored if resuming)
+        resume_session_id: str | None  — continue a prior CLI session
+        timeout: int = 3600            — hard timeout for the subprocess
+    """
+    try:
+        body = await request.json()
+    except json.JSONDecodeError:
+        return web.json_response({"error": "invalid JSON body"}, status=400)
+
+    prompt = body.get("prompt") or ""
+    if not prompt.strip():
+        return web.json_response({"error": "prompt is required"}, status=400)
+    system = body.get("system")
+    resume_session_id = body.get("resume_session_id")
+    timeout = int(body.get("timeout") or 3600)
+
+    response = web.StreamResponse(
+        status=200,
+        reason="OK",
+        headers={
+            "Content-Type": "text/event-stream",
+            "Cache-Control": "no-cache, no-transform",
+            "Connection": "keep-alive",
+            # X-Accel-Buffering=no defeats nginx/traefik buffering — the
+            # FastAPI container proxies via httpx and forwards bytes as
+            # they arrive, but the inner header is harmless and makes
+            # browser-direct testing easier.
+            "X-Accel-Buffering": "no",
+        },
+    )
+    await response.prepare(request)
+
+    async def send_event(payload: dict[str, Any]) -> None:
+        line = f"data: {json.dumps(payload, ensure_ascii=False)}\n\n"
+        await response.write(line.encode("utf-8"))
+
+    try:
+        async for event in claude_session.query_streaming(
+            prompt,
+            system=system,
+            resume_session_id=resume_session_id,
+            timeout=timeout,
+        ):
+            await send_event(event)
+            if event.get("type") == "done" or event.get("type") == "error":
+                break
+    except asyncio.CancelledError:
+        # Client disconnected — bail cleanly.
+        logger.info("chat_start: client disconnected")
+    except Exception as e:
+        logger.exception("chat_start: streaming failed")
+        try:
+            await send_event({"type": "error", "message": str(e)})
+        except ConnectionResetError:
+            pass
+
+    try:
+        await response.write_eof()
+    except ConnectionResetError:
+        pass
+    return response
+
+
+def build_app() -> web.Application:
+    app = web.Application()
+    app.router.add_get("/health", health)
+    app.router.add_post("/chat/start", chat_start)
+    return app
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description="legal-chat-service")
+    parser.add_argument("--port", type=int, default=8770)
+    parser.add_argument("--host", default="127.0.0.1",
+                        help="bind address; 127.0.0.1 keeps the service "
+                             "loopback-only — leave it alone in production")
+    parser.add_argument("--log-level", default="INFO")
+    args = parser.parse_args()
+
+    logging.basicConfig(
+        level=args.log_level.upper(),
+        format="%(asctime)s %(name)s %(levelname)s %(message)s",
+    )
+
+    app = build_app()
+    web.run_app(app, host=args.host, port=args.port, print=lambda _msg: None)
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())