feat(v0.2): tab status dot, activity (unread) indicator, drag-reorder

- terminal-session.ts: track SessionStatus (connecting/connected/reconnecting/
  exited) + onStatus callback; FIX: wire onTitleChange (onTitle was in opts but
  never bound — auto-title was dead)
- tabs.ts: per-tab status dot (color = connection state), unread flag set on
  background output + cleared on activate, HTML5 drag-to-reorder (preserves
  active tab, persisted)
- style.css: .tab-dot colors, .unread ring, .dragging/.drag-over feedback
- Browser-verified: green dot connected, unread ring after bg output, reorder
  AAA|BBB→BBB|AAA persists across reload. 191 tests green, typechecks + build ok.

public/terminal-session.ts

@@ -34,6 +34,9 @@ function buildWsUrl(): string {
   return `${scheme}://${location.host}/term`
 }
 
+/** Connection state, surfaced as a colored status dot on the tab. */
+export type SessionStatus = 'connecting' | 'connected' | 'reconnecting' | 'exited'
+
 export interface TerminalSessionOpts {
   /** Existing session to re-attach to, or null to spawn a fresh one. */
   sessionId: string | null
@@ -43,6 +46,8 @@ export interface TerminalSessionOpts {
   onActivity?: () => void
   /** Optional: fired when the terminal title changes (OSC 0/2 — cwd/process). */
   onTitle?: (title: string) => void
+  /** Optional: fired when connection status changes (for the tab status dot). */
+  onStatus?: (status: SessionStatus) => void
 }
 
 export class TerminalSession {
@@ -53,6 +58,9 @@ export class TerminalSession {
   private readonly resizeObserver: ResizeObserver
   private readonly onSessionId: (id: string) => void
   private readonly onActivity: (() => void) | undefined
+  private readonly onTitle: ((title: string) => void) | undefined
+  private readonly onStatus: ((status: SessionStatus) => void) | undefined
+  private statusValue: SessionStatus = 'connecting'
 
   private ws: WebSocket | null = null
   private sessionId: string | null
@@ -69,6 +77,8 @@ export class TerminalSession {
     this.sessionId = opts.sessionId
     this.onSessionId = opts.onSessionId
     this.onActivity = opts.onActivity
+    this.onTitle = opts.onTitle
+    this.onStatus = opts.onStatus
 
     this.el = document.createElement('div')
     this.el.className = 'term-pane'
@@ -84,6 +94,7 @@ export class TerminalSession {
     this.term.open(this.el)
 
     this.term.onData((data) => this.send(data))
+    this.term.onTitleChange((title) => this.onTitle?.(title))
 
     this.resizeObserver = new ResizeObserver(() => this.scheduleResize())
     this.resizeObserver.observe(this.el)
@@ -94,6 +105,16 @@ export class TerminalSession {
     return this.sessionId
   }
 
+  /** Current connection status (for the tab status dot). */
+  get status(): SessionStatus {
+    return this.statusValue
+  }
+
+  private setStatus(s: SessionStatus): void {
+    this.statusValue = s
+    this.onStatus?.(s)
+  }
+
   /** fit() only when the pane has real dimensions (display:none → NaN, §9). */
   private safefit(): { cols: number; rows: number } | null {
     try {
@@ -129,6 +150,7 @@ export class TerminalSession {
   connect(): void {
     if (this.disposed || this.isConnecting) return
     this.isConnecting = true
+    this.setStatus('connecting')
     this.term.write(statusLine(`${YELLOW}Connecting…${RESET}`))
 
     const socket = new WebSocket(buildWsUrl())
@@ -136,6 +158,7 @@ export class TerminalSession {
 
     socket.addEventListener('open', () => {
       this.reconnectDelay = 1000
+      this.setStatus('connected')
       this.term.write(statusLine(`${GREEN}${BOLD}Connected${RESET}`))
       socket.send(buildMessage({ type: 'attach', sessionId: this.sessionId }))
     })
@@ -176,6 +199,7 @@ export class TerminalSession {
         break
       }
       case 'exit': {
+        this.setStatus('exited')
         const reason = msg.reason ? ` (${msg.reason})` : ''
         this.term.write(
           statusLine(
@@ -200,6 +224,7 @@ export class TerminalSession {
 
   private scheduleReconnect(): void {
     if (this.reconnectTimer !== null) return
+    this.setStatus('reconnecting')
     const delay = this.reconnectDelay
     this.reconnectDelay = Math.min(this.reconnectDelay * 2, 30_000)
     this.term.write(