E01 · F04 · AUD-007 — Audit F04: free rotation of shapes

Full check of F04 in depth and of the project in breadth, following audit.md (ADR-0020), with the /audit skill.

Acceptance criteria

• Given the functions of F04, when audited, then every formula is re-derived, every expected value recomputed by hand, and each function survives a mutation spot-check.
• Given the sources, when audited, then every @see of F04 is re-verified online and dated.
• Given the project, when audited, then no duplicate, no copied code and no inconsistency between code, domain, ADRs and docs remains unrecorded.

Tasks

One task = one commit, referenced as AUD-007.Tn.

• T1 — A. Independent review by the auditor subagent; mathematics, mutation spot-checks, missing properties (2 h)
• T2 — B to H. Sources, provenance, duplicates, consistency, quality gates, research list for the next feature, light evolvability check; findings table (1.5 h)

Findings (2026-10-12)

Independent review by the auditor subagent (sections A to E, on a copy of the committed tree), mutation spot-checks by the agent (A4). Each story of F04 had its own review before (pull requests #122 to #127).

Check	Result	Evidence	Action
A1, A2 — derivations and expected values	correct	DERIV-turned-shape steps 1–5 and DERIV-arc-bounding-box steps 1–4 re-derived; every value of the feature's tests and test cards recomputed	—
A4 — one mutation per function (14)	all caught	degreesInTurn modulo (7 tests), turnDirection sign of sin (4), turnAbout sign (4), arcAxisPoints direction (1), contourBoundingBox arc filter (3), boxToViewBox margin (4), turnedCorners center (11), isShapeAngle bound (5), isShapePlacement y (1), positionKeepingPoint sign (10), positionAfterResize corner (2), freeShapeKeptInPlace local y (4), freeShapeContour move (12), regularPolygonContour position (1)	—
A3 — degreesInTurn	a dead + 0, a false comment	the inner sum lies in (0, 720): never a negative zero (probe over ±1e5)	fixed: removed, the TSDoc says why
A3 — positionAfterResize at 0°	early return unobservable	the general path gives the same position (100 000 random cases)	no action: kept, nothing computed at 0° as for every straight shape
A5 — properties	missing for four functions; turned edits only at 90°	positionKeepingPoint, arcAxisPoints, boxToViewBox; midpoint, deletion and conversion of a turned shape	added: properties at any angle
B — sources	reachable, quotes verbatim	9 URLs re-opened on 2026-10-12	—
C — provenance	written from the derivations	no library pattern, no dependency added	—
D1 — duplicates	box center computed three times; 360 declared twice	turnedCorners, positionAfterResize, freeShapeWithPoint; degreesInTurn, isShapeAngle	fixed: boxCenter, DEGREES_PER_TURN
E1 — a width emptied, then retyped	the turned shape jumped	a refused draw dropped the turned box kept	fixed: only a refused angle drops it; test
E1 — ADR-0034	changed by ADR-0035 without saying so	a coordinate typed on a turned shape is an integer in the drawing only	fixed: status lines, index, domain (Q27, Q28, shapes.md)
E1 — TSDoc saying "as drawn" for straight corners	contradicted turnedCorners	freeShapeCorners, freeShapeAroundCorners, rectangle and polygon corners, midpoint, deletion	fixed
E1 — snapping to the integer grid	to reconcile with a fractional stored position	interaction.md §4	noted there: the straight box's x and y are snapped
F — quality gates	green	check:all, 627 tests, coverage 100 % of src/	—

G. Next feature

F05 (text), next in E01's order, needs for its spike:

• SVG 2 text: <text>, x, y, text-anchor (start, middle, end), font-family, font-size in user units, fill; how dominant-baseline places the line (the baseline, not the top).
• Its straight box: without reading font files (ADR-0002), the box of a text cannot be computed by the core; a browser's getBBox measures it. How the editor shows it, and whether it is needed before E13's layout box.
• A turned text (F04): transform="rotate(…)" on <text>, the only primitive turned by SVG rather than computed; the angle and position of ADR-0035 for a text.
• Fonts available offline and the same in every browser (generic families, a font embedded in the library?): a Product Owner question.
• Integer size, color as for the shapes (E04 strokes and fills not there yet).

H. Light evolvability check

Question	Answer
Size	105 modules in src/ (model 49, geometry 30, math 15, io 6, render 5), 627 tests; the subfolders of model are due (improvement log)
Tools	StrykerJS still blocked; 14 mutations by hand, all caught
Fitness functions	the playground coverage threshold of CHK-007 still to do
Patterns	boxCenter now the one center of a turn: the movable center of E02 changes one place
Agent configuration	pitfalls of CHK-007 still true; nothing new
Process	the stories' reviews caught most findings; the audit found the gaps between stories (a width retyped, ADR-0034, "as drawn")