v1.1 batch 1: markdown, message actions, tok/s+ctx, AI naming

Four features land together on this branch:

1. Markdown rendering — assistant messages go through react-markdown +
   remark-gfm. Fenced code blocks render via existing CodeBlock (with copy
   button); inline `code` is styled inline. User messages stay plain text.
   No raw HTML (no rehype-raw).

2. Per-message Copy + Regenerate. New endpoint
   POST /api/sessions/:id/messages/:message_id/regenerate validates the
   target (404/400/409), atomically deletes the target plus any later
   messages in the session, inserts a fresh streaming assistant row, and
   enqueues a normal inference run. The DELETE bound uses a SQL subquery
   (`created_at >= (SELECT created_at FROM messages WHERE id = $1)`)
   instead of a JS round-trip so postgres TIMESTAMPTZ µs precision is
   preserved — otherwise sub-ms clock_timestamp() differences between the
   user row and the assistant row collapsed to the same JS Date, pulling
   the triggering user message into the >= bound. New `messages_deleted`
   WS frame so already-connected clients prune the stale tail without
   needing a full snapshot resend.

3. tok/s + ctx counter. Five new nullable message columns: tokens_used,
   ctx_used, ctx_max, started_at, finished_at. started_at is set right
   before the OpenAI call in services/inference.ts (not in the route, not
   in the frame handler); finished_at + tokens_used + ctx_used + ctx_max
   are committed in the same UPDATE that flips status to 'complete'. The
   inference request now opts into stream_options.include_usage so the
   final chunk carries usage; defensive parsing also picks up timings.n_ctx
   when llama.cpp emits it (currently absent for our llama-swap models, so
   ctx_max stays NULL and the UI just shows `<used> ctx`). message_complete
   frame extended with tokens_used / ctx_used / ctx_max / started_at /
   finished_at / model. Frontend StatsLine in MessageBubble computes tok/s
   client-side from the timestamps and renders muted mono text below the
   body of completed assistant messages.

4. AI chat naming after the first turn. Backend services/auto_name.ts
   runs via setImmediate after the top-level inference resolves; it
   checks that there is exactly one completed assistant message and that
   the session has not been user-renamed (`name IS NULL OR name = '' OR
   name = 'New session'`), then fires a single non-streaming chat
   completion with the spec prompt. Qwen3 chat templates emit chain-of-
   thought into reasoning_content and burn the entire max_tokens budget
   without producing visible output, so the request includes
   `chat_template_kwargs: { enable_thinking: false }` and max_tokens=30.
   Title is trimmed, quote-stripped, "Title:" prefix dropped, and
   truncated to 60 chars before a guarded UPDATE on sessions.name. New
   `session_renamed` WS frame propagates to the open session view
   directly and to the project's session list via a tiny module-scope
   event bus (apps/web/src/hooks/sessionEvents.ts) — kept dumb: one event
   type, two methods, no library.

Cleanups: dropped the now-unused splitCodeBlocks export from CodeBlock.tsx
(react-markdown supersedes it), and added a long-form NOTE in auto_name.ts
documenting the enable_thinking + max_tokens pattern for any future Qwen-
family non-streaming utility calls (planned: fork-message, agent-routing,
web-search summarization).

Schema bootstrap remains idempotent (ADD COLUMN IF NOT EXISTS). Auth,
broker, clock_timestamp() conventions, and zod validation all unchanged.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/components/CodeBlock.tsx

@@ -42,36 +42,3 @@ export function CodeBlock({ code, lang }: Props) {
     </div>
   );
 }
-
-interface SegmentText {
-  kind: 'text';
-  value: string;
-}
-interface SegmentCode {
-  kind: 'code';
-  lang?: string;
-  value: string;
-}
-export type Segment = SegmentText | SegmentCode;
-
-export function splitCodeBlocks(input: string): Segment[] {
-  const segments: Segment[] = [];
-  const fence = /```([a-zA-Z0-9_-]*)\n([\s\S]*?)```/g;
-  let lastIndex = 0;
-  let match: RegExpExecArray | null;
-  while ((match = fence.exec(input)) !== null) {
-    if (match.index > lastIndex) {
-      segments.push({ kind: 'text', value: input.slice(lastIndex, match.index) });
-    }
-    segments.push({
-      kind: 'code',
-      lang: match[1] || undefined,
-      value: (match[2] ?? '').replace(/\n$/, ''),
-    });
-    lastIndex = match.index + match[0].length;
-  }
-  if (lastIndex < input.length) {
-    segments.push({ kind: 'text', value: input.slice(lastIndex) });
-  }
-  return segments;
-}