Two more KNNTS041 viewer fixes:
1. Phantom-frame fast-forward. `buildFrames` now flags every frame
whose shot landed on an already-empty defender group as
`phantom: true`. During play the BattleViewer effect detects a
phantom frame and chains a 0 ms timer to the next non-phantom,
so streaks of phantoms (the ~30 frames between shots 224 and
255, and the 401..414 stretch) collapse from "the player just
mots the timeline" into a single visual tick. Step controls and
the scrubber can still land on a phantom deliberately for
protocol inspection.
2. Final-frame layout freeze. `displayFrame` derives from the raw
`frames[i]` and, on the very last frame when `activeRaceIds`
shrinks vs the penultimate frame (the killing blow eliminates a
race), substitutes the penultimate's `remaining` and
`activeRaceIds` while keeping the current `shotIndex` and
`lastAction`. The result: the surviving cluster no longer
reflows onto the planet ring on the very last shot — the user
sees the killing line + defender flash rendered against the
picture they saw a moment earlier.
Tests: `phantom-destroy clamp` case extended with `frame.phantom`
flag assertions across the protocol; 644 Vitest cases stay green,
4 Playwright `battle-viewer` cases stay green.
Docs: `ui/docs/battle-viewer-ux.md` documents the fast-forward
behaviour and the final-frame freeze.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Ilia Denisov
2e7478f5ea