feat: Read My Mind phase 2, the predictor and the brain button

The feature as pitched in docs/readmymind-plan.md: pressing the header
brain button predicts the prompt you were about to type, from the case's
intent profile plus everything the session already knows.

Backend:
- readmymind-context.ts: pure budgeted context assembler (9 ranked
  sources: pending approval dialog, user goals, last assistant turn tail,
  recent prompts, tool activity, git workspace signals, away context,
  sibling sessions, rethink state; 30 KB budget, whole-section drop from
  the bottom of the ranking, trust tiers stated in the prompt)
- readmymind-collectors.ts: transcript tail reader (the live watcher
  keeps only a 500-char snippet) and git signal collection (execFile,
  2s timeout, skipped for remote-SSH cases)
- readmymind-predictor.ts: one-shot claude -p in a throwaway tmux
  session, opus by default (readMyMindModel setting), strict JSON
  contract with 1-3 suggestions (continue / verify / redirect), newline
  stripping, 90s timeout; mutable singleton so route tests can stub it
- POST /api/sessions/:id/readmymind: claude-mode only (400), one
  prediction in flight per session (409 CONFLICT), rethink body
  { steer, rejected }; ownership via findSessionOrFail

Frontend:
- readmymind-ui.js (loadorder 11.3): header brain button, marker-hidden
  until readMyMindEnabled is ON, desktop only (phone key is phase 3);
  modal with editable suggestion + rationale and Send / Insert /
  Rethink / Dismiss; suggestion text rendered via value/textContent only
  and nothing ever auto-sends
- App Settings -> Panels checkbox for readMyMindEnabled; en + zh-CN
  strings

Verified end to end against a live isolated instance: transcript
capture, a real opus prediction grounded in the stated goals, rethink
steering, the 409, and the browser modal incl. Insert leaving the text
unsubmitted on the composer. 41 new unit/route tests; full test:ci
sweep green (4680 tests).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/web/routes/readmymind-routes.ts

@@ -1,11 +1,12 @@
 /**
- * @fileoverview Read My Mind intent routes.
+ * @fileoverview Read My Mind routes: intent profiles + the predictor.
  *
  * Per-case intent profiles feeding the Read My Mind predictor
  * (docs/readmymind-plan.md):
  * - `GET    /api/sessions/:id/intent`: the profile for the session's case
  * - `PUT    /api/sessions/:id/intent`: replace the goals text
  * - `DELETE /api/sessions/:id/intent`: forget the case's profile
+ * - `POST   /api/sessions/:id/readmymind`: predict the user's next prompt
  *
  * The profile is keyed by owner + workingDir, so multi-user scoping is
  * structural; session ownership is still enforced via `findSessionOrFail`
@@ -16,6 +17,15 @@
  * the session resolves owner + workingDir server-side, so a caller can never
  * address another case's profile by guessing keys.
  *
+ * Predict gathers every signal Codeman already has (intent profile, pending
+ * approval dialog, transcript tail, git state, run-summary events, sibling
+ * sessions), assembles a budgeted prompt via the pure
+ * `buildPredictionContext()`, and runs the one-shot predictor. Claude-mode
+ * only (400: capture and transcripts exist for nothing else), one prediction
+ * in flight per session (409 CONFLICT), and suggestions are only ever
+ * RETURNED, never sent: the human click in the modal is the boundary, which
+ * is also the prompt-injection mitigation for observed content.
+ *
  * Registrations use the bare `app.<method>('path', ...)` + `req.params as`
  * shape (session-routes style): these endpoints are documented in the agent
  * skill, and the endpoints.md drift test's scanner does not see registrations
@@ -23,12 +33,21 @@
  */
 
 import { FastifyInstance } from 'fastify';
-import { IntentGoalsSchema } from '../schemas.js';
+import { ApiErrorCode, createErrorResponse } from '../../types.js';
+import { IntentGoalsSchema, ReadMyMindPredictSchema } from '../schemas.js';
 import { parseBody, findSessionOrFail } from '../route-helpers.js';
 import { intentStore } from '../../intent-store.js';
-import type { SessionPort } from '../ports/index.js';
+import { approvalInbox } from '../approval-inbox.js';
+import { hooksAvailableForMode } from '../session-wait-registry.js';
+import { buildPredictionContext, type PredictionContextInputs } from '../../readmymind-context.js';
+import { collectWorkspaceSignals, readTranscriptSignals } from '../../readmymind-collectors.js';
+import { readMyMindPredictor } from '../../readmymind-predictor.js';
+import type { ConfigPort, InfraPort, SessionPort } from '../ports/index.js';
 
-export function registerReadMyMindRoutes(app: FastifyInstance, ctx: SessionPort): void {
+/** One prediction in flight per session; a second POST while running is a 409. */
+const predictionsInFlight = new Set<string>();
+
+export function registerReadMyMindRoutes(app: FastifyInstance, ctx: SessionPort & ConfigPort & InfraPort): void {
   app.get('/api/sessions/:id/intent', async (req) => {
     const { id } = req.params as { id: string };
     const session = findSessionOrFail(ctx, id, req);
@@ -47,4 +66,73 @@ export function registerReadMyMindRoutes(app: FastifyInstance, ctx: SessionPort)
     const session = findSessionOrFail(ctx, id, req);
     return { success: true, data: { deleted: intentStore.deleteProfile(session.owner, session.workingDir) } };
   });
+
+  app.post('/api/sessions/:id/readmymind', async (req, reply) => {
+    const { id } = req.params as { id: string };
+    const body = parseBody(ReadMyMindPredictSchema, req.body ?? {});
+    const session = findSessionOrFail(ctx, id, req);
+
+    if (!hooksAvailableForMode(session.mode)) {
+      reply.code(400);
+      return createErrorResponse(ApiErrorCode.INVALID_INPUT, 'Read My Mind predicts claude-mode sessions only');
+    }
+    if (predictionsInFlight.has(id)) {
+      reply.code(409);
+      return createErrorResponse(ApiErrorCode.CONFLICT, 'A prediction is already running for this session');
+    }
+
+    predictionsInFlight.add(id);
+    try {
+      const profile = intentStore.getProfile(session.owner, session.workingDir);
+      const pending = approvalInbox.getForSession(id);
+      const transcriptPath = ctx.getTranscriptPath(id);
+      const transcript = transcriptPath ? await readTranscriptSignals(transcriptPath) : null;
+      // Remote-SSH cases skip git: workingDir is not local. Docker cases are
+      // fine (the workspace is bind-mounted at the same host path).
+      const workspace = session.remote ? null : await collectWorkspaceSignals(session.workingDir);
+
+      const lastPromptTs = profile.recentPrompts[profile.recentPrompts.length - 1]?.ts;
+      const tracker = ctx.runSummaryTrackers.get(id);
+      const awayEvents = (tracker?.getRecentEvents(15) ?? [])
+        .filter((ev) => lastPromptTs === undefined || ev.timestamp >= lastPromptTs)
+        .map((ev) => ({ timestamp: ev.timestamp, title: ev.title, details: ev.details }));
+
+      const siblings = [...ctx.sessions.values()]
+        .filter((s) => s.id !== id && s.workingDir === session.workingDir && s.status !== 'stopped')
+        .map((s) => ({ name: s.name, mode: s.mode, working: s.isWorking }));
+
+      const inputs: PredictionContextInputs = {
+        pendingDialog: pending
+          ? {
+              kind: pending.kind,
+              toolName: pending.toolName,
+              message: pending.message,
+              context: pending.context,
+              options: pending.options,
+            }
+          : undefined,
+        goals: profile.goals,
+        lastAssistantText: transcript?.lastAssistantText ?? undefined,
+        recentPrompts: profile.recentPrompts.map((p) => ({ ts: p.ts, text: p.text })),
+        recentTools: transcript?.recentTools,
+        workspace: workspace ?? undefined,
+        awaySinceMs: lastPromptTs !== undefined ? Date.now() - lastPromptTs : undefined,
+        awayEvents,
+        siblings,
+        steer: body.steer,
+        rejected: body.rejected,
+      };
+
+      const { prompt } = buildPredictionContext(inputs);
+      const model = await ctx.getReadMyMindModel();
+      const result = await readMyMindPredictor.predict({ sessionId: id, prompt, model });
+      return { success: true, data: { suggestions: result.suggestions, durationMs: result.durationMs } };
+    } catch (err) {
+      reply.code(502);
+      const message = err instanceof Error ? err.message : 'Prediction failed';
+      return createErrorResponse(ApiErrorCode.OPERATION_FAILED, message);
+    } finally {
+      predictionsInFlight.delete(id);
+    }
+  });
 }