fix(desktop): stop the tool row repeating its command three times

The expanded terminal row printed the same string as the title, as the
`$` transcript, and again as detail. shellCommand preferred the
backend's display preview over the real `command` arg, so the transcript
showed a summary of what ran rather than what ran; and a terminal call
with no output fell through to the generic fallback, which echoes
args.context under a transcript already showing it.

apps/desktop/src/components/assistant-ui/tool/fallback-model.test.ts

@@ -340,6 +340,28 @@ describe('buildToolView title actions', () => {
     expect(view.titleAction).toEqual({ prefix: '', text: 'Running', suffix: ' pnpm run lint' })
   })
 
+  it('never stutters the verb or echoes the command when the backend context is a phrased label', () => {
+    // Older backends stamped tool.start with a *phrased* label
+    // ("Running sleep 70 + 2 commands") rather than a raw arg preview, and the
+    // desktop merges that into args.context. The row must still prepend its own
+    // verb exactly once, show the real command in the `$` transcript, and not
+    // repeat either string as detail.
+    const command = 'sleep 70; echo "a"; echo "b"'
+
+    const view = buildToolView(
+      part({
+        args: { command, context: 'Running sleep 70 + 2 commands' },
+        result: { exit_code: 0 },
+        toolName: 'terminal'
+      }),
+      ''
+    )
+
+    expect(view.title).toBe('Ran sleep 70 + 2 commands')
+    expect(view.terminalCommand).toBe(command)
+    expect(view.detail).toBe('')
+  })
+
   it('uses the runtime locale for title text and action placement', () => {
     setRuntimeI18nLocale('ja')
 

apps/desktop/src/components/assistant-ui/tool/fallback-model/index.ts

@@ -128,9 +128,14 @@ function readFileDisplayTarget(args: Record<string, unknown>, result: Record<str
   return [fileEditBasename(path), lineLabel].filter(Boolean).join(' ')
 }
 
+// The real command, preferring the actual argument over the backend's
+// display preview. `context` is a *summarized* preview ("sleep 70 + 2
+// commands") the gateway sends on tool.start before real args arrive — fine
+// as a placeholder for the live title, wrong for the `$` transcript, which
+// must show what actually ran.
 function shellCommand(args: Record<string, unknown>): string {
   return (
-    firstStringField(args, ['context', 'preview']) || firstStringField(args, ['command', 'code']) || contextValue(args)
+    firstStringField(args, ['command', 'code']) || firstStringField(args, ['context', 'preview']) || contextValue(args)
   )
 }
 
@@ -1079,6 +1084,13 @@ function toolDetailText(
     if (output || lines) {
       return [output, lines].filter(Boolean).join('\n')
     }
+
+    // A terminal row with no output already shows its command in the `$`
+    // transcript above; the generic fallback would print the same string a
+    // second time. `execute_code` has no transcript, so it keeps the fallback.
+    if (part.toolName === 'terminal') {
+      return ''
+    }
   }
 
   if (part.toolName === 'web_extract') {