fix(native-chat): give the projected Diff row the file-change glyph

Every Codex fileChange item projects to a tool call named `Diff`, which the
edit set does not name — it names the tools that carry the edit in their own
input. So a run whose body renders an edited-file card was headed by the
generic wrench.

src/renderer/src/components/native-chat/NativeChatToolRun.test.tsx

@@ -456,6 +456,29 @@ describe('NativeChatToolRun', () => {
     ).toEqual(['lucide-chevron-right'])
   })
 
+  it('heads a projected diff run with the file-change glyph, not the generic one', () => {
+    const projected = projectStructuredItemToNativeChat({
+      itemId: 'file-change',
+      revision: 1,
+      sequence: 1,
+      observedAt: 1,
+      body: {
+        kind: 'diff',
+        path: 'src/a.ts',
+        patch: { head: '@@ -1 +1 @@\n-was\n+now', truncated: false, byteLength: 24 }
+      }
+    })
+
+    const { container } = render(
+      <NativeChatToolRun blocks={projected?.blocks ?? []} expandSignal={false} expandOverride />
+    )
+
+    // The run renders an edited-file card, so a wrench above it reads as a tool
+    // this vocabulary does not model.
+    expect(container.querySelector('.lucide-pencil')).toBeInTheDocument()
+    expect(container.querySelector('.lucide-wrench')).toBeNull()
+  })
+
   it('labels a bare list row by the command it ran rather than an invented path', () => {
     const blocks: NativeChatBlock[] = [
       {

src/shared/native-chat-tool-icon.test.ts

@@ -67,6 +67,13 @@ describe('native chat tool icons', () => {
     }
   })
 
+  it('reads the projected `Diff` row as a file change, which is what it renders', () => {
+    // Every Codex fileChange item projects to a call named `Diff`, so a wrench
+    // here headed a run whose body is an edited-file card.
+    expect(nativeChatToolCategory('Diff')).toBe('fileChange')
+    expect(nativeChatToolIconName('Diff')).toBe('pencil')
+  })
+
   it('reads an MCP tool by its prefix, since the row is named after the tool', () => {
     expect(nativeChatToolCategory('mcp__linear__create_issue')).toBe('mcpToolCall')
     expect(nativeChatToolIconName('mcp__playwright__browser_click')).toBe('plug')

src/shared/native-chat-tool-icon.ts

@@ -65,6 +65,9 @@ const CATEGORY_BY_ROW_WORD = new Map<string, NativeChatToolCategory>([
   ['read', 'read'],
   ['search', 'search'],
   ['list', 'listFiles'],
+  // Every Codex file change projects as a `Diff` call, and the edit set below
+  // names the tools that carry the edit in their input, not that projection.
+  ['diff', 'fileChange'],
   // Claude's tool names, which its lane renders verbatim.
   ['grep', 'search'],
   ['glob', 'search'],