fix(tui): give inline_diff segments blank-line breathing room

Visual polish on top of the segment-anchor change: diff blocks were
butting up against the narration around them. Tag diff-only segments
with `kind: 'diff'` (extended on Msg) and give them `marginTop={1}` +
`marginBottom={1}` in MessageLine, matching the spacing we already
use for user messages. Also swaps the regex-based `diffSegmentBody`
check for an explicit `kind === 'diff'` guard so the dedupe path is
clearer.

ui-tui/src/__tests__/createGatewayEventHandler.test.ts

@@ -165,19 +165,19 @@ describe('createGatewayEventHandler', () => {
     // Diff is already committed to segmentMessages as its own segment —
     // nothing is "pending" anymore. The pre-tool narration is also flushed.
     expect(appended).toHaveLength(0)
-    expect(turnController.segmentMessages.map(m => m.text)).toEqual([
-      'Editing the file',
-      `\`\`\`diff\n${cleaned}\n\`\`\``
+    expect(turnController.segmentMessages).toEqual([
+      { role: 'assistant', text: 'Editing the file' },
+      { kind: 'diff', role: 'assistant', text: `\`\`\`diff\n${cleaned}\n\`\`\`` }
     ])
 
     onEvent({ payload: { text: 'patch applied' }, type: 'message.complete' } as any)
 
     // Three messages in the transcript, in order: pre-tool narration →
-    // diff → post-tool narration. The final message does NOT contain
-    // `diff` content.
+    // diff (kind='diff' so MessageLine gives it blank-line breathing room)
+    // → post-tool narration. The final message does NOT contain a diff.
     expect(appended).toHaveLength(3)
     expect(appended[0]?.text).toBe('Editing the file')
-    expect(appended[1]?.text).toBe(`\`\`\`diff\n${cleaned}\n\`\`\``)
+    expect(appended[1]).toMatchObject({ kind: 'diff', text: `\`\`\`diff\n${cleaned}\n\`\`\`` })
     expect(appended[2]?.text).toBe('patch applied')
     expect(appended[2]?.text).not.toContain('```diff')
   })
@@ -214,6 +214,7 @@ describe('createGatewayEventHandler', () => {
 
     // diff segment first, final narration second
     expect(appended).toHaveLength(2)
+    expect(appended[0]?.kind).toBe('diff')
     expect(appended[0]?.text).not.toContain('┊ review diff')
     expect(appended[0]?.text).toContain('--- a/foo.ts')
     expect(appended[1]?.text).toBe('done')
@@ -247,9 +248,10 @@ describe('createGatewayEventHandler', () => {
     } as any)
     onEvent({ payload: { text: 'done' }, type: 'message.complete' } as any)
 
-    // Two segments: diff block (no tool row), final narration (tool row
-    // belongs here since pendingSegmentTools carries across the flush).
+    // Two segments: diff block (kind='diff', no tool row), final narration
+    // (tool row belongs here since pendingSegmentTools carries across the flush).
     expect(appended).toHaveLength(2)
+    expect(appended[0]?.kind).toBe('diff')
     expect(appended[0]?.text).toContain('```diff')
     expect(appended[0]?.tools ?? []).toEqual([])
     expect(appended[1]?.text).toBe('done')

ui-tui/src/app/turnController.ts

@@ -19,17 +19,16 @@ const INTERRUPT_COOLDOWN_MS = 1500
 const ACTIVITY_LIMIT = 8
 const TRAIL_LIMIT = 8
 
-// Matches segments produced by pushInlineDiffSegment — a bare ```diff fence
-// wrapping the raw patch, no surrounding prose. Used at message.complete to
-// dedupe against final assistant text that narrates the same patch.
-const DIFF_SEGMENT_RE = /^```diff\n([\s\S]*?)\n```$/
-
+// Extracts the raw patch from a diff-only segment produced by
+// pushInlineDiffSegment. Used at message.complete to dedupe against final
+// assistant text that narrates the same patch. Returns null for anything
+// else so real assistant narration never gets touched.
 const diffSegmentBody = (msg: Msg): null | string => {
-  if (msg.role !== 'assistant' || msg.tools?.length) {
+  if (msg.kind !== 'diff') {
     return null
   }
 
-  const m = msg.text.match(DIFF_SEGMENT_RE)
+  const m = msg.text.match(/^```diff\n([\s\S]*?)\n```$/)
 
   return m ? m[1]! : null
 }
@@ -226,7 +225,7 @@ class TurnController {
       return
     }
 
-    this.segmentMessages = [...this.segmentMessages, { role: 'assistant', text: block }]
+    this.segmentMessages = [...this.segmentMessages, { kind: 'diff', role: 'assistant', text: block }]
     patchTurnState({ streamSegments: this.segmentMessages })
   }
 

ui-tui/src/components/messageLine.tsx

@@ -81,11 +81,16 @@ export const MessageLine = memo(function MessageLine({
     return <Text {...(body ? { color: body } : {})}>{msg.text}</Text>
   })()
 
+  // Diff segments (emitted by pushInlineDiffSegment between narration
+  // segments) need a blank line on both sides so the patch doesn't butt up
+  // against the prose around it.
+  const isDiffSegment = msg.kind === 'diff'
+
   return (
     <Box
       flexDirection="column"
-      marginBottom={msg.role === 'user' ? 1 : 0}
-      marginTop={msg.role === 'user' || msg.kind === 'slash' ? 1 : 0}
+      marginBottom={msg.role === 'user' || isDiffSegment ? 1 : 0}
+      marginTop={msg.role === 'user' || msg.kind === 'slash' || isDiffSegment ? 1 : 0}
     >
       {showDetails && (
         <Box flexDirection="column" marginBottom={1}>

ui-tui/src/types.ts

@@ -102,7 +102,7 @@ export interface ClarifyReq {
 
 export interface Msg {
   info?: SessionInfo
-  kind?: 'intro' | 'panel' | 'slash' | 'trail'
+  kind?: 'diff' | 'intro' | 'panel' | 'slash' | 'trail'
   panelData?: PanelData
   role: Role
   text: string