feat(agent): temporal video dedup — drop near-duplicate frames before the GPU

Near-static videos are the dominant GPU load: sampled into up to 64 frames, each
re-runs the whole detect→CCIP→SigLIP chain on ~identical content. Add a CPU
perceptual-hash frame dedup upstream of the GPU so the redundant frames are never
processed at all (not just their embeds).

- media.dedupe_frames() + _dhash(): 8×8 difference-hash (64-bit) per frame; greedy
  keep — a frame survives only if its hash differs from every kept frame by
  >= min_distance bits (Hamming). A static run collapses to one frame; genuinely
  distinct scenes all survive. Order + frame_time preserved.
- Called in worker._download_decode right after sample_frames, so it runs in the
  decode stage on the downloader thread (CPU) — the GPU consumers only ever see
  deduped frames, and buffered video items shrink (less RAM too).
- Env-tunable FRAME_DEDUPE_DISTANCE (default 8; higher keeps more frames for brief
  localized changes an 8×8 hash can miss; 0 disables). Logs `video frames N→M`
  when it drops any, so video load reduction is visible.

Complements the spatial per-frame crop dedup (2026-07-01.2); this is the temporal
axis. Build marker 2026-07-01.3.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ttrj5P7upUTueSfoJcxEqa

agent/fc_agent/app.py

@@ -17,7 +17,7 @@ from .worker import Worker
 # Bump on every agent change. The page embeds this and /status reports it; the UI
 # warns to reload when they differ — so a stale browser-cached page can't be
 # mistaken for "the new image didn't deploy". (Belt-and-braces with no-store.)
-VERSION = "2026-07-01.2 · crop dedup before embed"
+VERSION = "2026-07-01.3 · video frame dedup"
 
 logbuf.install()
 cfg = Config.from_env()