Summary

• Brings irrelevant-sections-redact.ts from 15.67% → 91.79% statements (0% → 100% functions). The rule is now the last untested-rule item cleared from the ratchet comment.
• Mocks LLM calls at the llm-client boundary — the rule talks to the background worker through chrome.runtime.connect, so mocking the port-side function avoids needing chrome/fetch mocks. Two additional boundary mocks unbreak ts-jest's CJS transform (nanoid, abort-utils) and a third (../lib/availability) breaks a rules-barrel circular import that bites single-rule loads.
• Extracts jsdom shims (Element.checkVisibility, offsetWidth/Height) to src/__test-mocks__/jsdom-extras.ts wired via Jest's setupFiles, so any future test that touches page-tree or visibility-aware code picks them up automatically.
• Ratchets ./src/rules/ thresholds 84/71/88/84 → 90/77/95/90 to lock in the gain.

What the tests cover

• Lifecycle: apply → waitForSettle → classify → DOM mutation; teardown discards late responses; scroll triggers debounced reclassify; scroll burst coalesces.
• Response processing: refs resolve to elements; summary surfaces in placeholder label; default label when summary missing; placeholder height capped.
• Dedupe: repeated refs in one response; ancestor + descendant collapse to outermost; unresolvable refs skipped.
• Hideability protections: skips <article> / <header> / [role="banner"] descendants; skips position: fixed / position: sticky; skips elements taller than 70% viewport.
• Errors: empty page tree short-circuits before LLM call; AbortError swallowed; generic error swallowed.

Test plan

• bun run preflight passes (lint + typecheck + knip + jest with coverage)
• Coverage summary shows ~83% statements / 74% branches / 85% functions
• ./src/rules/ threshold check passes at the new 90/77/95/90 floor

🤖 Generated with Claude Code