feat(browser): within/excludeSelector/list_form_fields + stuck guard (1.8.2)

[Rippy1911]

Summary

Closes the four tooling holes that killed the Base44 “Per-Page Meta Tags” grind (2026-08-03): chat-column noise, unlabeled per-row pencils, no form inventory, and silent observation loops.

Changes

• F2 get_interactive({ within: { text|selector } }) — post-scan row scope; absolute item.i preserved for click_index
• F3 excludeSelector on get_page / find_text / get_interactive — prune CSS subtrees (chat sidebars, cookie walls)
• F4 list_form_fields — fillable field inventory with resolved labels; password hasValue only; same i handles as get_interactive
• F5 Semantic stuck guard — warn at 6 observation-only calls, block at 9; reset on mutation or URL change
• F6 Stop checkpoint — on abort with open todo/doing tasks, transcript line: Stopped. Tasks: N/M done; last action: …
• Version bump 1.8.2

Acceptance matrix

Form	Test file	Result
get_interactive({within:{text:"Row3"}}) → exactly that row’s pencil with absolute i; click_index works	packages/core/src/browser/rowScope.test.ts	✅ pass
find_text({excludeSelector:"aside"}) drops chat hits, keeps workspace	packages/core/src/browser/rowScope.test.ts	✅ pass
get_page({excludeSelector:"aside"}) prunes chat column	packages/core/src/browser/rowScope.test.ts	✅ pass
list_form_fields maps 3 labeling styles + password never leaks value	packages/core/src/browser/rowScope.test.ts	✅ pass
Stuck guard warns at 6 varied reads; mutation resets; changing URL does not trip	packages/core/src/agent/repeatGuard.test.ts	✅ pass
Loop: 6-read streak warns; click resets; subsequent read clean	packages/core/src/agent/loopGuards.test.ts	✅ pass
Stop checkpoint with open tasks + last mutation	packages/core/src/agent/loopGuards.test.ts	✅ pass
pnpm typecheck && pnpm test && pnpm build	CI local	✅ green (661 tests)

Hard rules

• Absolute-index contract preserved (within/excludeSelector are post-scan filters on get_interactive)
• No new MV3 permissions
• Tool descriptions updated with concrete examples (models discover params through them)