fix(web): keep ready subissue labels visible

[teloverge]

What changed

• Keep ready subissue labels visible when their outward geometry grazes only their own padded star obstacle.
• Preserve collision avoidance against every other star and previously placed label.
• Add a canvas-level regression that checks label visibility and rendered-ring clearance through 20 real camera-easing frames.
• Declare npm 12.0.2 as the web workspace development package manager and activate it before all nine CI, bundle, and release npm ci steps.
• Add a job-scoped workflow contract that rejects cross-job setup borrowing and enforces the nine-step inventory.
• Record both pending changes in the Unreleased changelog.

Root cause

The outward label geometry already cleared its own rendered star and emphasis ring, but the generic collision pass compared its padded reservation with that same star's square obstacle. On diagonal spokes those conservative boxes could graze, causing the ready label to disappear.

The first CI run also showed that Node 24 runners currently provide npm 11.16.0, which correctly rejected the intentional npm 12.0.2 development-engine requirement. Each workflow now activates the declared npm version before dependency installation.

Validation

• npm test — 28 files, 225 tests passed
• npm run check — 0 errors and 0 warnings
• npm run build — production build passed
• npm toolchain contract — 9 workflow install paths verified
• Windows, macOS, Linux packaging contracts — passed
• Release-boundary contract — passed
• Independent pre-merge review — no Critical or Important findings after amendments