fix: sync run button state with terminal process via centralized exit tracking

Centralize terminal process lifecycle in terminal-context as single
source of truth. TerminalView reports exit/failure via callback,
context maintains exitedTerminals set, command-dropdown reacts to it.

Removes redundant polling and per-component exit event subscriptions
that raced with deferred spawn introduced in b2d10fa.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/terminal/terminal-panel.tsx

@@ -5,7 +5,7 @@ import { TerminalTabBar } from "./terminal-tab-bar"
 import { TerminalView } from "./terminal-view"
 
 export function TerminalPanel() {
-  const { isOpen, tabs, activeTabId } = useTerminalContext()
+  const { isOpen, tabs, activeTabId, markTerminalExited } = useTerminalContext()
 
   return (
     <section
@@ -22,6 +22,7 @@ export function TerminalPanel() {
             initialCommand={tab.initialCommand}
             isActive={tab.id === activeTabId}
             isVisible={isOpen}
+            onProcessExited={markTerminalExited}
           />
         ))}
       </div>

src/components/terminal/terminal-view.tsx

@@ -95,6 +95,7 @@ interface TerminalViewProps {
   initialCommand?: string
   isActive: boolean
   isVisible: boolean
+  onProcessExited?: (terminalId: string) => void
 }
 
 export function TerminalView({
@@ -103,6 +104,7 @@ export function TerminalView({
   initialCommand,
   isActive,
   isVisible,
+  onProcessExited,
 }: TerminalViewProps) {
   const containerRef = useRef<HTMLDivElement>(null)
   const fitAddonRef = useRef<{ fit: () => void } | null>(null)
@@ -110,6 +112,7 @@ export function TerminalView({
   const lastResizeRef = useRef<{ cols: number; rows: number } | null>(null)
   const isActiveRef = useRef(isActive)
   const isVisibleRef = useRef(isVisible)
+  const onProcessExitedRef = useRef(onProcessExited)
   const [loading, setLoading] = useState(true)
 
   useEffect(() => {
@@ -117,6 +120,10 @@ export function TerminalView({
     isVisibleRef.current = isVisible
   }, [isActive, isVisible])
 
+  useEffect(() => {
+    onProcessExitedRef.current = onProcessExited
+  }, [onProcessExited])
+
   useEffect(() => {
     let cancelled = false
     let cleanup: (() => void) | undefined
@@ -188,6 +195,7 @@ export function TerminalView({
       const unlistenExit = await subscribe<TerminalEvent>(
         `terminal://exit/${terminalId}`,
         () => {
+          onProcessExitedRef.current?.(terminalId)
           term.write("\r\n\x1b[90m[Process exited]\x1b[0m\r\n")
         }
       )
@@ -206,6 +214,7 @@ export function TerminalView({
       try {
         await terminalSpawn(workingDir, initialCommand, terminalId)
       } catch (err) {
+        onProcessExitedRef.current?.(terminalId)
         term.write(`\r\n\x1b[31m[Failed to start terminal: ${err}]\x1b[0m\r\n`)
       } finally {
         if (!cancelled) setLoading(false)