fix(host/windows): don't 2-way-split-encode Main10 — it's SLOWER on Ada (fixes broken HDR animations)

The "broken animations in HDR" was an encode-throughput cliff, not the ACCESS_LOST churn. Measured at
5120x1440@240 HEVC Main10 on the RTX 4090: forced 2-way split-encode = 7.6 ms/frame (~131 fps, well
over the 4.17 ms/240fps budget → choppy), while SINGLE engine = 2.8-3.9 ms/frame (~256-357 fps, fits
240). The split/merge overhead dominates for 10-bit; a single Ada NVENC engine already handles 5K@240
Main10 comfortably. So the split decision now forces DISABLE for Main10 (bit_depth >= 10), keeping the
existing forced-2 only for 8-bit above 1 Gpix/s. PUNKTFUNK_SPLIT_ENCODE still overrides. Added a
split-mode log line.

Validated live on the 4090: encode_us_p50 7.6 ms → 3.9 ms at 5K240 HDR with no env override.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Cargo.toml

@@ -5,6 +5,7 @@ members = [
     "crates/punktfunk-host",
     "crates/punktfunk-client-rs",
     "crates/punktfunk-client-linux",
+    "crates/punktfunk-client-windows",
     "crates/punktfunk-android",
     "tools/latency-probe",
     "tools/loss-harness",