Fix HALO border continuity at rounded corners

[soojy]

Fix the HALO border dash that gets cut at the top-left corner when the rounded perimeter is not an exact multiple of the dash pattern. Fit whole dash cycles to the perimeter while preserving the dash/gap ratio and animation speed.

Recalculate spacing only when dimensions change and reuse one two-element array per mounted surface. The draw-call count, canvas sizes, shadows, scheduler and visibility policy stay unchanged. Other frontend edits only refresh content-hashed imports and manifest entries.

Validation:

• All 56 offline Python tests passed; all 11 JavaScript modules passed syntax checks; frontend compatibility/import/hash checks passed.
• Browser checks passed across six resize cases (360 frames), verifying whole-cycle closure, dash proportions and reuse of the same array.
• Synchronized before/after browser preview verified corner continuity.
• Local real-Canvas benchmark, alternating order, 2 warm-up + 10 measured batches of 20 frames: 12 nodes at 584×536 measured median 2.205 → 2.180 ms/frame at DPR 1 and 2.310 → 2.215 ms/frame at DPR 2. Single-node cases also showed no regression. These are JS/Canvas submission timings, not GPU trace or end-to-end FPS measurements; differences are within run noise.

Video previews

Actual HALO renderer with enlarged corners. Click either animated preview to play the full MP4. Watch the synchronized side-by-side comparison.

Before

After