feat(lint): add needle_pivot_offset hub-referenced layout check

[xuanruli]

What it catches

A gauge needle / clock hand / dial pointer / radar sweep that rotates about the wrong pivot — the recovered center-of-rotation sits far from the dial hub (e.g. transform-origin at the needle base or SVG element edge instead of the dial center). Visually the needle "wobbles" or orbits off-axis instead of sweeping cleanly about the hub.

This is a genuine gap in the current checks: rotation_pivot_drift (#2741) provably cannot catch it — a correct sweeping needle's bbox-center orbits identically to a broken one, so only a dial-hub reference distinguishes them. This is the separate hub-referenced check that analysis called for.

How it works

• Sampler maps 2 material endpoints per frame via getScreenCTM (honors the actual rendered transform, independent of svgOrigin).
• Resolves the dial hub = shared center of the modal set of static concentric circles, or the arc-center of the largest static near-circular path (Kasa circle fit).
• Fits a circle to the endpoint trajectory to recover the true center-of-rotation; flags drift > 0.35 * pointer_length. One warning per hub.
• Never fires without a resolvable hub. Walks the rotation reference to the composition root (not the <svg>) so a pointer rotated by a div ancestor is measured correctly.
• Multi-body guard: >= 2 bodies at distinct angular positions on one hub = orbit/atom system, not a dial → suppressed.

Corpus evidence (autonomous geometry-fuzz run, 81 fuzzed diagrams)

• 7 / 7 true positives, 0 false positives across all 81 samples.
• Assigned TPs: fuzz005, fuzz017, fuzz032. Bonus TPs: fuzz044, fuzz056, fuzz068, fuzz080.
• The Gemini-3.6 video-judge itself MISSED all 4 bonus TPs (vlm_has_defects: false) — the deterministic hub-reference check beats the VLM on this defect class.
• FPs driven to 0 by the two principled guards above: fuzz016 (planet arc rotated by a div ancestor) cleared by root-walk; fuzz055 (atom) cleared by the multi-body guard.
• fuzz080 reads as a false positive to the connector check but is a true positive here — confirms the architectural boundary between the two checks is drawn correctly.

Validation

• Autonomous Gemini-3.6 video-judge fuzz run to surface candidate defects, then a deterministic FP sweep across all 81 rendered compositions (not VLM-gated — code inspection is the arbiter, since the VLM both over- and under-calls this class).
• 9 unit tests (checkPipeline.needlePivotOffset.test.ts) + full check suite pass; bun run build green.

🤖 Generated with Claude Code

[github-actions]

Fallow audit report

Found 14 findings.

Duplication (12)

Severity	Rule	Location	Description
minor	fallow/code-duplication	packages/cli/src/commands/check.test.ts:323	Code clone group 1 (13 lines, 2 instances)
minor	fallow/code-duplication	packages/cli/src/commands/check.test.ts:358	Code clone group 1 (13 lines, 2 instances)
minor	fallow/code-duplication	packages/cli/src/commands/layout-audit.browser.js:1586	Code clone group 2 (13 lines, 2 instances)
minor	fallow/code-duplication	packages/cli/src/commands/layout-audit.browser.js:1601	Code clone group 3 (8 lines, 2 instances)
minor	fallow/code-duplication	packages/cli/src/utils/checkBrowser.ts:477	Code clone group 4 (6 lines, 2 instances)
minor	fallow/code-duplication	packages/cli/src/utils/checkBrowser.ts:501	Code clone group 4 (6 lines, 2 instances)
minor	fallow/code-duplication	packages/cli/src/utils/checkPipeline.needlePivotOffset.test.ts:43	Code clone group 5 (8 lines, 2 instances)
minor	fallow/code-duplication	packages/cli/src/utils/checkPipeline.needlePivotOffset.test.ts:89	Code clone group 5 (8 lines, 2 instances)
minor	fallow/code-duplication	packages/cli/src/utils/checkPipeline.ts:558	Code clone group 6 (24 lines, 2 instances)
minor	fallow/code-duplication	packages/cli/src/utils/checkPipeline.ts:683	Code clone group 2 (13 lines, 2 instances)
minor	fallow/code-duplication	packages/cli/src/utils/checkPipeline.ts:700	Code clone group 3 (8 lines, 2 instances)
minor	fallow/code-duplication	packages/cli/src/utils/checkPipeline.ts:714	Code clone group 6 (24 lines, 2 instances)

Health (2)

Severity	Rule	Location	Description
minor	fallow/high-crap-score	packages/cli/src/utils/checkBrowser.ts:509	'parseNeedlePivotSample' has CRAP score 31.6 (threshold: 30.0, cyclomatic 10)
minor	fallow/high-cognitive-complexity	packages/cli/src/utils/checkPipeline.ts:804	'detectNeedlePivotOffset' has cognitive complexity 21 (threshold: 15)

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