Show the Brain beside the AI chat and make schedules from chosen material

The Brain and AI page lists Brain material (failed documents hidden) with
search, open, delete and per-material or select-all ticks. New schedules use
only the ticked material, kept through topic edits and resumes; nothing ticked
means the whole Brain. With material ticked, the agent skips the content topic
question and names the material in the chat and plan.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/express/schedules.test.ts

@@ -63,6 +63,17 @@ describe('content language', () => {
   })
 })
 
+describe('chosen material', () => {
+  it('marks a schedule made from chosen material in its brief, and reads it back as chosen', () => {
+    const r = rule('summary', 2, 'week', 'sales', 'Bahasa Indonesia')
+    const config = configFor(r, 0, true)
+    expect(config.instructions).toMatch(/Use only the Brain material chosen for this schedule\./)
+    expect(configFor(r).instructions).not.toMatch(/chosen/)
+    expect(ruleOf(agentFrom(config))).toEqual({ ...r, chosen: true })
+    expect(ruleOf(agentFrom(configFor(r)))).toEqual(r)
+  })
+})
+
 describe('ruleOf', () => {
   it.each([
     rule('summary', 3),