Gate `tv-ui-60fps` + `input-latency` + `boot-to-home-screen`: frame-time histogram thresholds, key-to-photon via capture, golden-frame screenshot suite in QEMU x86

Epic: #113 · Milestone: MC7 — TV shell

Tasks

• QEMU x86 golden suite: every screen state captured via the QEMU monitor and compared with a perceptual tolerance; runs per PR (ui-golden job).
• tv-ui-60fps on the rig: scripted 30 s navigation over a 500-item grid via the phone API; histogram from perf; p99 ≤ 16.6 ms, zero frames > 33 ms.
• input-latency: the CEC adapter sends a key while the capture runs; a screen region flips colour on key handling; frames between the send timestamp and the flip → ≤ 50 ms.
• boot-to-home-screen: power-cycle to first interactive frame (detected by a corner marker) ≤ 8 s.
• Floors in scripts/perf-floors.json; status page table.

Acceptance

All three gates pass on two consecutive weekly runs.

Size: S · Depends on: #92, #98, #100, #49 · Blocks: v1