feat(ui+perf): d3d11va decode, muted-cell audio skip, cohesive theme + slicker wizard/cells

[tcconnally]

Slicker UI + measured decode performance

A UI-polish + performance pass on top of v10.0.0. Every perf change was A/B-measured on skyhawk (RTX 5070 Ti, 8-cell 2×2×2 wall) — no speculative tuning.

⚡ Performance

Decode path: nvdec-copy → d3d11va (default). d3d11va decodes straight into the D3D11 textures the gpu-next/d3d11 renderer consumes — no surface copy-back to system RAM like nvdec-copy, and none of the CUDA↔D3D11 interop cost that made non-copy nvdec worse. HYPERWALL_HWDEC override retained as an escape hatch.

hwdec	GPU mem	CPU/24s	power	frame-drops
nvdec-copy (old)	~3.25 GB	~6 s	~49 W	0–1
nvdec (non-copy)	~1.9 GB	~28 s ❌	~49 W	0
d3d11va (new)	~2.25 GB	~4–7 s	~46 W	0

The robust, repeatable win is ~30% less VRAM (two passes) at equal CPU/power/smoothness — directly easing the roadmap's memory-scaling concern for large grids. (CPU/RAM deltas beyond that were within content-variance noise, since clips are randomized per run; not claimed.)

Muted cells skip audio decode. The wall is muted by default; cells now load with aid=no, so the grid doesn't demux/decode audio it never plays. The track is lazily (re)selected on first unmute via _enable_audio_track() — no reload.

🎨 UI

• hyperwall/theme.py — one source of truth: palette (keeps the on-brand #3b8edb accent shared with the web remote), typography, radii, a dialog QSS, and a Fusion dark QPalette so native chrome (message boxes, combos) matches. Pure strings, no Qt import at load → headless-test friendly.
• Cell control bar — glassy translucent slab; borderless, rounded, quiet buttons that lift to the accent on hover/active; slimmer accent seek slider.
• Title card → translucent pill with an accent spine. Startup shows a pulsing LOADING card that animates only before the first frame — never during steady playback (keeps the 24/7 idle cost at zero).
• Setup wizard — themed, branded header, accent selection highlights, a live ROWS×COLS grid preview + "N cells / display" readout, and Enter-to-start.

Wizard (new)

(screenshot attached in comment)

✅ Validation

• python tests/run_all.py → 85/85 green (added tests/test_theme.py for the pure helpers).
• Rebuilt hyperwall.exe; launched on skyhawk: log confirms hwdec=d3d11va, NVIDIA profile current, G-Sync isolation intact, all cells play [DIRECT]/[TRANSCODE] with no Playback error / Stall / Crash-loop.
• Cell UI + wizard visually verified via off-screen render + PrintWindow (content-free).

No behavior change to playback semantics, reliability chain, backends, or the web remote.

[tcconnally]

📸 Screenshots (couldn't inline-embed via gh CLI) are saved on skyhawk for review — drag them into this PR to embed:

• Wizard: C:\Users\tccon\Downloads\hyperwall_wizard_new.png — branded HYPERWALL header + accent subtitle, themed DISPLAYS/SOURCES panels with accent selection, and the new LAYOUT row: themed spinboxes, live 2×2 grid preview, "4 cells / display" readout, INITIALIZE button.
• Cell UI: C:\Users\tccon\Downloads\hyperwall_cell_ui_new.png — glass control bar with quiet rounded buttons (⭐ shown in its accent "checked" state), slim accent seek, and the title pill with the accent spine, over a black frame (content-free capture).

[tcconnally]

Added: monochrome control-bar icons, color only when active (commit ef360d6).

• All transport/loop/mute glyphs forced to text-presentation (VS15) so they render monochrome and inherit the bar tint.
• The favorite star lights up gold when the item is a favorite, and the trash bin turns red when flagged for deletion (VS16 color glyph) — reverting to monochrome when inactive. Fav/trash also drop the accent :checked fill so the colored glyph is the sole active signal.

Refreshed cell screenshot on skyhawk (favorite active = gold star, everything else monochrome): C:\Users\tccon\Downloads\hyperwall_cell_ui_new.png.

Verified: 85/85 tests green, rebuilt exe smoke-launched clean (hwdec=d3d11va, cells playing, no errors).