docs: handoff section in browse template + TODOS update

Add User Handoff section to browse/SKILL.md.tmpl with usage examples.
Update State Persistence TODO noting saveState/restoreState reusability.

TODOS.md

@@ -52,7 +52,9 @@
 
 **Why:** Enables "resume where I left off" for QA sessions and repeatable auth states.
 
-**Effort:** M
+**Context:** The `saveState()`/`restoreState()` helpers from the handoff feature (browser-manager.ts) already capture cookies + localStorage + sessionStorage + URLs. Adding file I/O on top is ~20 lines.
+
+**Effort:** S
 **Priority:** P3
 **Depends on:** Sessions
 

browse/SKILL.md.tmpl

@@ -106,6 +106,32 @@ $B diff https://staging.app.com https://prod.app.com
 ### 11. Show screenshots to the user
 After `$B screenshot`, `$B snapshot -a -o`, or `$B responsive`, always use the Read tool on the output PNG(s) so the user can see them. Without this, screenshots are invisible.
 
+## User Handoff
+
+When you hit something you can't handle in headless mode (CAPTCHA, complex auth, multi-factor
+login), hand off to the user:
+
+```bash
+# 1. Open a visible Chrome at the current page
+$B handoff "Stuck on CAPTCHA at login page"
+
+# 2. Tell the user what happened (via AskUserQuestion)
+#    "I've opened Chrome at the login page. Please solve the CAPTCHA
+#     and let me know when you're done."
+
+# 3. When user says "done", re-snapshot and continue
+$B resume
+```
+
+**When to use handoff:**
+- CAPTCHAs or bot detection
+- Multi-factor authentication (SMS, authenticator app)
+- OAuth flows that require user interaction
+- Complex interactions the AI can't handle after 3 attempts
+
+The browser preserves all state (cookies, localStorage, tabs) across the handoff.
+After `resume`, you get a fresh snapshot of wherever the user left off.
+
 ## Snapshot Flags
 
 {{SNAPSHOT_FLAGS}}