## Summary
Fixes#4226 (Release Blocker, V32 regression).
The WebGL nuke trajectory preview built its SAM threat set by
unconditionally excluding own + allied SAMs
(`BuildPreviewController.updateNukeTrajectoryPreview`). But when the
strike targets allied territory, the alliance breaks at launch —
`NukeExecution.maybeBreakAlliances()` — so the betrayed ally's SAMs
**do** engage the nuke. The preview therefore showed a fully white
trajectory with no intercept X over an allied SAM, even though the bomb
would be shot down (V31 previewed this correctly).
## Fix
- Compute the would-be-betrayed player set with
`listNukeBreakAlliance()` — the exact function the sim uses at launch,
so preview and sim can't drift.
- Keep an allied SAM in the threat set iff its owner is in that set
(extracted as pure `samThreatensNukePreview()`).
- Other (non-betrayed) allies' SAMs remain excluded, matching sim
behavior where only alliances over the blast threshold break.
Both missing artifacts in the issue (red post-intercept segment and X
marker) come from `tSamIntercept` staying at 1.0 because no SAM was
supplied, so this one change restores both.
Cost note: this adds one `circleSearch` per throttled ghost update
(50ms) when the player has allies — same order as the existing
`wouldNukeBreakAlliance` call for the red warning circle.
## Testing
- Unit tests for the new threat-set predicate (4 cases) in
`tests/client/controllers/BuildPreviewController.test.ts`
- `tsc --noEmit`, ESLint, Prettier clean
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
UILayer → WarshipSelectionController and StructureIconsLayer →
BuildPreviewController. These are the two real Controller implementations
(state + click handling, no rendering) — the new names + location reflect
what they actually do now that all rendering lives in WebGL passes.
Evan