fix(session): learn the live Claude conversation from the CLI's own hook

Which conversation a pane is on was re-derived by correlating
~/.claude/history.jsonl against Session.lastSubmitAt — and lastSubmitAt is
bumped only by input that flows through Codeman's own write path
(Session.write / writeViaMux). A user who attaches to the pane's tmux session
directly never set it, so resolveActiveClaudeSessionIdFromHistory() returned at
its first line for that pane's whole life and the response viewer stayed pinned
to the launch conversation, showing a pre-/clear transcript indefinitely.

A UserPromptSubmit hook reports the live conversation id from inside the CLI
process, delivered under the pane's own $CODEMAN_SESSION_ID. That binding is a
fact rather than a correlation: it never consults workingDir, so it cannot be
claimed by a sibling pane on the same folder, a closed tab, or a bare `claude`
in the user's terminal. A pane holding such an id skips the correlation
entirely, so the number of prompts eligible for cwd-based guessing goes DOWN,
never up — the naive alternative (relax the guard, or synthesize an anchor from
PTY activity) is the reverted bug the resolver's own comment describes.

The hook also stamps lastSubmitAt, so it finally means "a prompt was submitted"
rather than "typed into Codeman's web terminal". Conversations vouched for
first-hand — and only those — extend a persisted claudeSessionChain, whose tail
re-pins the conversation when a surviving tmux session is re-attached after a
restart. ⚠️ start() resets the id at THREE points and the last one runs
unconditionally after the mux branch, so the tail is applied there too; patching
only the mux branch looks right and silently does nothing.

⚠️ The hook's stdout is discarded with curl's own -o /dev/null. Claude Code
injects a UserPromptSubmit hook's stdout into the model's context ("Exit code 0
- stdout shown to Claude"), and a trailing >/dev/null does NOT work: curlCmd
already ends `... 2>/dev/null || true`, and in `pipeline || true >/dev/null` the
shell binds the redirection to `true`, which never runs on the success path. The
discard is opt-in so the five SSE-fed events keep byte-identical command text
and no workspace's settings file is rewritten for them. The staleness marker is
quote-free for the matching reason: hooksJson is JSON.stringify'd, so a quoted
needle never matches and the gate would rewrite every workspace on every spawn.

Existing workspaces heal on their next Claude spawn through the staleness sweep.

src/web/route-helpers.ts

@@ -422,6 +422,11 @@ export function sanitizeHookData(data: Record<string, unknown> | null | undefine
     'stop_hook_active',
     'transcript_path',
     'message',
+    // UserPromptSubmit identity fields. `prompt` is deliberately NOT here: the
+    // prompt text would land in the SSE broadcast, and Read My Mind already
+    // captures intent through transcript-watcher.
+    'prompt_id',
+    'source',
   ];
 
   for (const key of allowedKeys) {

src/web/routes/hook-event-routes.ts

@@ -129,7 +129,29 @@ export function registerHookEventRoutes(
     if (data && typeof data.session_id === 'string' && data.session_id) {
       const session = ctx.sessions.get(sessionId);
       const prevClaudeSessionId = session?.claudeSessionId;
-      session?.adoptClaudeSessionId(data.session_id);
+      const prevChainLength = session?.claudeSessionChain.length ?? 0;
+      // FIRST-HAND: this payload came from the CLI process itself and reached us
+      // because the pane's own $CODEMAN_SESSION_ID addressed it. No cwd, no
+      // timestamp, nothing a sibling pane on the same folder could win — so the
+      // response viewer can stop guessing entirely (see
+      // resolveActiveClaudeSessionIdFromHistory).
+      session?.adoptClaudeSessionId(data.session_id, { firstHand: true });
+      if (event === 'prompt_submitted') {
+        // Repairs `lastSubmitAt` for a pane driven straight from tmux: it was
+        // bumped only by input that flowed through Codeman's own write path, so
+        // it read 0 forever for those panes and every consumer of "when did this
+        // pane last submit" silently degraded.
+        session?.markPromptSubmitted();
+      }
+      // Persist when the conversation actually moved: `/clear` emits no
+      // completion event, so without this the successor id is lost on restart
+      // and recovery falls back to the launch conversation.
+      if (
+        session &&
+        (session.claudeSessionId !== prevClaudeSessionId || session.claudeSessionChain.length !== prevChainLength)
+      ) {
+        ctx.persistSessionState(session);
+      }
       // Docker sessions: keep the case's resume seed following the LIVE
       // conversation (post-/clear id switches), so a container stop/reboot
       // relaunch resumes the right transcript.

src/web/routes/session-routes.ts

@@ -1860,8 +1860,17 @@ export function registerSessionRoutes(
     session: Session,
     projectsDir: string
   ): Promise<string | null> {
+    // A pane whose conversation id came from its OWN hook needs no correlation:
+    // $CODEMAN_SESSION_ID (the pane's env) -> data.session_id (the CLI's own
+    // stdin JSON) is a first-hand binding that never looks at cwd, so it cannot
+    // be stolen by a sibling pane, a closed tab, or a bare `claude` in a
+    // terminal. Guessing can only be worse than the fact. This is also what
+    // closes the hole below for a pane driven straight from tmux: it never
+    // reaches `if (!submitAt)`.
+    if (session.claudeSessionIdIsFirstHand) return null;
+
     const submitAt = session.lastSubmitAt;
-    if (!submitAt) return null; // never typed through Codeman — nothing to credit
+    if (!submitAt) return null; // no anchor at all — nothing to credit
     const cached = claudeHistoryPinCache.get(session.id);
     if (cached && cached.submitAt === submitAt) return cached.claudeSessionId;
 

src/web/schemas.ts

@@ -924,6 +924,9 @@ export const HookEventSchema = z.object({
     'stop',
     'teammate_idle',
     'task_completed',
+    // Claude Code's UserPromptSubmit: a first-hand report of the pane's live
+    // conversation id. Keep in step with HookEventType in types/api.ts.
+    'prompt_submitted',
     // A turn STARTED. Unlike the others this one has no Claude Code hook behind
     // it: it is reported by the DeepSeek Harness status shim, and exists so a
     // dialog answered in the terminal resolves its Approvals Inbox item at once

src/web/server.ts

@@ -2794,6 +2794,10 @@ export class WebServer extends EventEmitter {
               // the launch conversation until the user types again, even though
               // the re-attached CLI is on a post-`/clear` one.
               lastSubmitAt: savedState?.lastSubmitAt,
+              // Conversations this pane provably owned, oldest first. Its tail is
+              // the conversation the CLI was on when the server stopped, which is
+              // what a re-attach must point the viewer at instead of the launch id.
+              claudeSessionChain: savedState?.claudeSessionChain,
               // The pane's last output, previous run's value. Without it every
               // restart restamped all sessions "now" (constructor + the attach
               // repaint within the same second), flattening the home screens'