docs: rewrite README + skills docs, auto-invoke /document-release (v0.8.4) (#207)

* docs: add 6 missing skills to proactive suggestion list

Add /codex, /careful, /freeze, /guard, /unfreeze, /gstack-upgrade to the
root SKILL.md.tmpl proactive suggestion list so Claude suggests them at
the appropriate workflow stages.

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

* docs: add 6 new skill entries + browse handoff to docs

- docs/skills.md: add /codex, /careful, /freeze, /guard, /unfreeze,
  /gstack-upgrade to skill table with deep-dive sections. Group safety
  skills into one "Safety & Guardrails" section. Add browse handoff
  subsection to /browse deep-dive.
- BROWSER.md: add handoff/resume to command reference table + section.

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

* docs: add power tools section + update skill lists in README

- Update prose: "Fifteen specialists and six power tools"
- Add power tools table after sprint specialists: /codex, /careful,
  /freeze, /guard, /unfreeze, /gstack-upgrade
- Update all 4 skill list locations (install Step 1, Step 2,
  troubleshooting CLAUDE.md example) to include all 21 skills

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

* docs: add v0.7-v0.8.2 features to README "What's new" section

Add paragraphs for browse handoff, /codex multi-AI review, safety
guardrails (/careful, /freeze, /guard), proactive skill suggestions,
and /ship auto-invoking /document-release.

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

* feat: auto-invoke /document-release after /ship PR creation

Add Step 8.5 to /ship that automatically reads document-release/SKILL.md
and executes the doc update workflow after creating the PR. This prevents
documentation drift — /ship now keeps docs current without a separate
command.

Completes P1 TODO: "Auto-invoke /document-release from /ship"

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

* chore: bump version and changelog (v0.8.4)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

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

BROWSER.md

@@ -17,6 +17,7 @@ This document covers the command reference and internals of gstack's headless br
 | Tabs | `tabs`, `tab`, `newtab`, `closetab` | Multi-page workflows |
 | Cookies | `cookie-import`, `cookie-import-browser` | Import cookies from file or real browser |
 | Multi-step | `chain` (JSON from stdin) | Batch commands in one call |
+| Handoff | `handoff [reason]`, `resume` | Switch to visible Chrome for user takeover |
 
 All selector arguments accept CSS selectors, `@e` refs after `snapshot`, or `@c` refs after `snapshot -C`. 50+ commands total plus cookie import.
 
@@ -123,6 +124,18 @@ The server hooks into Playwright's `page.on('console')`, `page.on('response')`,
 
 The `console`, `network`, and `dialog` commands read from the in-memory buffers, not disk.
 
+### User handoff
+
+When the headless browser can't proceed (CAPTCHA, MFA, complex auth), `handoff` opens a visible Chrome window at the exact same page with all cookies, localStorage, and tabs preserved. The user solves the problem manually, then `resume` returns control to the agent with a fresh snapshot.
+
+```bash
+$B handoff "Stuck on CAPTCHA at login page"   # opens visible Chrome
+# User solves CAPTCHA...
+$B resume                                       # returns to headless with fresh snapshot
+```
+
+The browser auto-suggests `handoff` after 3 consecutive failures. State is fully preserved across the switch — no re-login needed.
+
 ### Dialog handling
 
 Dialogs (alert, confirm, prompt) are auto-accepted by default to prevent browser lockup. The `dialog-accept` and `dialog-dismiss` commands control this behavior. For prompts, `dialog-accept <text>` provides the response text. All dialogs are logged to the dialog buffer with type, message, and action taken.