fix: migrate to chrome.debugger CDP for Turnstile compatibility

[ancs21]

Summary

• Replace page-context monkey-patching (injected.js) with Chrome DevTools Protocol via chrome.debugger API — eliminates all page-context modifications that trigger Cloudflare Turnstile and similar anti-bot systems
• Fix request tab scrolling for long content (closes Long content in Request tab get truncated and is not scrollable #1)
• Default view to "Group by domain" for better DX

What changed

File	Change
public/injected.js	Deleted — no more page-context injection
public/content.js	Stripped to DOM search/highlight only
public/background.js	Rewritten to use CDP Network/Fetch/Runtime domains
public/manifest.json	Added debugger permission, removed web_accessible_resources
src/sidepanel/App.tsx	Added port lifecycle, debugger status indicator, breakpoint banner, default grouped view
src/sidepanel/components/detail/RequestDetail.tsx	Fixed Request tab scroll overflow
CLAUDE.md	Updated architecture docs

How it works

• Network domain — passive capture of all XHR/Fetch requests with full response bodies
• Fetch domain — intercepts requests only when mock or breakpoint rules are active
• Runtime domain — captures console errors and unhandled exceptions
• Port lifecycle — debugger attaches when side panel opens, detaches on close (minimizes yellow infobar exposure)

Tradeoffs

• Chrome shows a yellow "debugging this browser" infobar when the debugger is attached — acceptable for a developer tool
• Only Network, Fetch, Runtime CDP domains are used (no Runtime.evaluate) to limit blast radius

Test plan

• Load extension, open side panel — yellow infobar appears, status dot turns green
• Browse pages — requests appear in side panel grouped by domain
• Visit a Cloudflare Turnstile-protected page — page loads normally (no challenge failure)
• Create a mock rule — matching requests return mock response
• Create a breakpoint rule — matching requests show pause banner in side panel, Continue/Cancel work
• Close side panel — yellow infobar disappears
• Open a request with large body — Request tab scrolls correctly
• Console errors appear in the console tab

🤖 Generated with Claude Code

Plan: docs/plans/2026-04-06-001-fix-cloudflare-turnstile-compatibility-plan.md