fix(orchestration): keep optional preamble sections out of Markdown headings

The sub-dispatch and base-drift sections end with a bare rule directly under a
paragraph, which Markdown parses as a setext H2, so the Chat UI rendered the
section's last sentence as a heading. The unfenced sub-dispatch commands also
lost their angle-bracket placeholders to the raw-HTML pass. Fence those
commands like the main CLI block and put a blank line before each closing rule.

src/main/runtime/orchestration/coordinator-task-dispatch.ts

@@ -132,7 +132,7 @@ export async function dispatchTaskToWorker(params: {
   let gateContext = ''
   if (gates.length > 0) {
     const latest = gates.at(-1)!
-    gateContext = `\n\n--- DECISION GATE RESOLVED ---\nQuestion: ${latest.question}\nResolution: ${latest.resolution}\n---\n`
+    gateContext = `\n\n--- DECISION GATE RESOLVED ---\nQuestion: ${latest.question}\nResolution: ${latest.resolution}\n\n---\n`
   }
 
   try {

src/main/runtime/orchestration/preamble.test.ts

@@ -31,6 +31,16 @@ function cliFence(result: string): string {
   return match?.[1] ?? ''
 }
 
+function markdownBlocks(result: string) {
+  const tree = unified().use(remarkParse).parse(result)
+  return {
+    headings: tree.children.filter((node) => node.type === 'heading'),
+    codeBlocks: tree.children.filter((node) => node.type === 'code')
+  }
+}
+
+const driftParams = { base: 'origin/main', behind: 3, recentSubjects: ['fix: a', 'feat: b'] }
+
 describe('buildDispatchPreamble', () => {
   it('substitutes template variables', () => {
     const result = buildDispatchPreamble(baseParams())
@@ -73,15 +83,36 @@ describe('buildDispatchPreamble', () => {
 
   it('fences shell comments so Markdown does not promote them to headings', () => {
     const result = buildDispatchPreamble(baseParams())
-    const tree = unified().use(remarkParse).parse(result)
-    const headings = tree.children.filter((node) => node.type === 'heading')
-    const codeBlocks = tree.children.filter((node) => node.type === 'code')
+    const { headings, codeBlocks } = markdownBlocks(result)
 
     expect(headings).toHaveLength(0)
     expect(codeBlocks).toHaveLength(1)
     expect(codeBlocks[0]).toMatchObject({ lang: 'sh', value: cliFence(result) })
   })
 
+  // Why: a `---` rule directly under a paragraph is a setext H2, so the optional
+  // sections' closing rules must not turn their last sentence into a heading.
+  it('renders no Markdown headings when the sub-dispatch and drift sections are present', () => {
+    const result = buildDispatchPreamble(
+      baseParams({ canDispatchSubWorkers: true, baseDrift: driftParams })
+    )
+    const { headings, codeBlocks } = markdownBlocks(result)
+
+    expect(headings).toHaveLength(0)
+    expect(codeBlocks).toHaveLength(2)
+    expect(codeBlocks[1]).toMatchObject({ lang: 'sh' })
+    expect(codeBlocks[1].value).toContain('orchestration worker-start --task <task_id>')
+    expect(result).toContain('able to dispatch further.\n\n---')
+    expect(result).toContain('before starting.\n\n---')
+  })
+
+  it('sub-dispatch fence passes bash -n', { timeout: 15_000 }, () => {
+    const result = buildDispatchPreamble(baseParams({ canDispatchSubWorkers: true }))
+    const { codeBlocks } = markdownBlocks(result)
+    const check = spawnSync('bash', ['-n'], { input: codeBlocks[1].value, encoding: 'utf8' })
+    expect(check.status).toBe(0)
+  })
+
   it('includes heartbeat CLI block with taskId and dispatchId and 5-minute cadence', () => {
     const result = buildDispatchPreamble(baseParams())
     expect(result).toContain('--type heartbeat')

src/main/runtime/orchestration/preamble.ts

@@ -196,6 +196,8 @@ work under the new Dispatch; ignore stale follow-ups from the settled task.`
 // Why the whole section is omitted rather than softened when nesting is off: a
 // worker told it "usually cannot" delegate still tries, then reports the refusal
 // as a blocker.
+// Why fenced + blank line before the closing `---`: unfenced `<placeholders>` are stripped as raw
+// HTML by the Chat UI, and a rule directly under a paragraph is a setext H2 (giant last sentence).
 function buildSubDispatchSection(cli: string): string {
   return `
 
@@ -203,13 +205,16 @@ function buildSubDispatchSection(cli: string): string {
 You may dispatch sub-workers for this task. Bind your own Run first, then create
 and start each one:
 
+\`\`\`sh
   ${cli} orchestration run-create --objective "<what the sub-workers are for>" --json
   ${cli} orchestration task-create --spec "<sub-task>" --json
   ${cli} orchestration worker-start --task <task_id> --worktree current --agent <agent> --json
+\`\`\`
 
 You own those sub-workers: wait for their worker_done, and do not report your own
 until they have settled. Nesting is capped, so a sub-worker of yours may not be
 able to dispatch further.
+
 ---`
 }
 
@@ -224,5 +229,6 @@ ${subjects}
 
 If any look relevant to your task, either pull them in (\`git pull --rebase
 ${drift.base}\` or equivalent) or escalate to the coordinator before starting.
+
 ---`
 }