#20657: Security: add length validation to browser evaluate function

## Summary - Add a 100KB max length check on evaluate function bodies in `pw-tools-core.interactions.ts` - The browser sandbox is the primary security boundary for `evaluateViaPlaywright`; this is defense-in-depth to limit oversized payloads - Clear security comment explaining the architecture ## Test plan - [ ] Run browser-related tests - [ ] Verify normal evaluate calls (typically <1KB) work as before - [ ] Verify oversized payloads (>100KB) are rejected with a clear error message 🤖 Generated with [Claude Code](https://claude.com/claude-code) <!-- greptile_comment --> <h3>Greptile Summary</h3> Added a 100KB max length check on evaluate function bodies in `evaluateViaPlaywright` to limit oversized payloads as defense-in-depth security measure. The implementation correctly validates before executing the function and provides a clear error message. **Key changes:** - Added `MAX_EVALUATE_FN_LENGTH` constant (100,000 bytes) - Length check with descriptive error message showing actual vs max size - Clear security comment explaining the defense-in-depth rationale **Issue found:** - `waitForViaPlaywright` also accepts function strings via `opts.fn` parameter on line 446 and passes them to `page.waitForFunction` without the same length validation, which is an inconsistency in the security boundary <h3>Confidence Score: 4/5</h3> - Safe to merge with one inconsistency to address: `waitForViaPlaywright` lacks the same length validation - The implementation is solid - correct validation placement, clear error messages, and good security comments. Score of 4 (not 5) due to incomplete coverage: `waitForViaPlaywright` on line 446 also accepts function strings but doesn't have the same length check, creating an inconsistency in the security boundary - Pay attention to `waitForViaPlaywright` function (line 446) which needs the same length validation for consistency _{Last reviewed commit: 7f52b4f} <!-- greptile_other_comments_section --> <!-- /greptile_comment -->