Fix debug panel persistence and controls

[claude-do]

Summary

Fix two regressions in the temporary user-input debug panel:

• only persist debug-panel visibility on dev hosts (t3-dev.claude.do / localhost)
• stop the draggable header from swallowing button presses for Collapse and Off

Problem

After production promotion, the debug panel could remain visible without the query param because the enabled state was persisted in localStorage. On mobile, the entire header was also acting as the drag handle, which prevented the action buttons from working reliably.

Fix

• gate persistence to dev-only hosts while still allowing the query param anywhere
• reduce the drag handle to the title area so the action buttons receive normal pointer/click events

Validation

• bun fmt
• bun lint (repo currently has unrelated warnings only)
• bun run --cwd apps/web build
• bun typecheck is currently failing in unrelated server/web-push work already present in the repo