Video core: low-priority hardening follow-ups from adversarial review of #125

[lstein]

Adversarial review of #125 (feat/video-panel-02-core) surfaced these low-priority items. The one medium finding (accelerator flag drifting when a LoRA is removed) is already handled by setLoras + the mount reconciler introduced in #127, so only edge residue remains.

1. Accelerator residue on reload after uninstall — if an accelerator LoRA is uninstalled between sessions, normalizeVideoSettings (features/video/core/settings.ts) clears acceleratorEnabled/acceleratorLoraKeys but keeps steps=4 / cfgScale=1 and leaves the surviving pair member as an ordinary user LoRA. Restore the model's sampling defaults there too (mirroring what setLoras does live).
2. Prototype-chain lookup in the variant matrix — baseEntry.variants[variant] ?? baseEntry.fallback (videoPolicies.ts ~237) resolves "constructor"/"toString" variants to Object.prototype members and then throws on config.modes.includes. Use Object.hasOwn or a null-prototype object.
3. findWanLightningLoraPair can mix families — high and low picks are independent (videoPolicies.ts ~459-465); with only [I2V High, T2V Low] installed it assembles a cross-family pair. Require both halves from the same family.
4. Unsanitized variant token in new RegExp (videoPolicies.ts ~456): a variant containing a regex metachar makes the constructor throw. Escape the token.
5. isValidWanNumFrames has no upper bound (dimensions.ts ~177) — accepts 165 despite WAN_NUM_FRAMES_MAX = 161. Masked because the exported isValidVideoNumFrames enforces the max; tighten the helper and its test anyway.
6. Banker's-rounding test gap — the only half-case tested is 22.5→22 (even floor); a round-half-down regression would pass the suite. Add an odd-floor half case (e.g. one that snaps 23.5→24). (Implementation itself was fuzz-verified correct against Python round().)
7. Stale cfgScale/steps across family switch when accelerator branch doesn't run (getVideoModelSelectionResult) — currently invisible+unvalidated for guidance-distilled H3; verify the graph builder never reads them in that state, or reconcile on switch.
8. Unsupported H3 main gets WAN fallback config in getVideoDimensions — preview-only cosmetic coercion of '768 lowres'→'720p'; invocation is blocked by isSupportedVideoModel. Also: VideoSourceClip trim bounds are only validated by the backend node.

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https://claude.ai/code/session_01LUjUcPHzQCoL7dqgsVzi63