feat(video): HDR10/P010 end to end (phase 6)

The client now advertises VIDEO_CAP_10BIT|HDR and carries the result all
the way to glass:

- csc_rows is bit-depth exact (10-bit limited code points differ from
  8-bit by ~half a code) and folds in the P010/X6 MSB-packing factor;
  new 10-bit white/black tests.
- The CSC shader grows a params block: mode 0 passes the transfer
  through (SDR as-is, or PQ onto an HDR10 swapchain); mode 1 tonemaps
  PQ→SDR in-shader (ST.2084 EOTF, 203-nit reference white exposure,
  BT.2020→709, soft maxRGB rolloff, sRGB encode) for desktops without
  an HDR surface. PUNKTFUNK_TONEMAP_PEAK tunes the rolloff.
- The presenter probes VK_EXT_swapchain_colorspace + an HDR10/ST.2084
  10-bit surface format and flips modes in-band with the stream's PQ
  signaling: fence-quiesce, then CSC pass + video image (10-bit
  A2B10G10R10 intermediate — PQ in 8 bits bands) + overlay pipe +
  swapchain rebuild through the deferred-destroy rules.
- P010 decodes through all three paths: Vulkan Video (X6 multiplanar
  pool, R10X6 plane views), VAAPI dmabuf (R16/RG1616 plane imports),
  software (swscale as before).
- session pump advertises the caps; the host still gates Main10 behind
  its PUNKTFUNK_10BIT policy.

Probed on glass hardware: the KDE/NVIDIA surface exposes
A2B10G10R10+HDR10_ST2084, so true PQ passthrough is available there.
Known v1 gaps: software-decode PQ shows untonemapped (8-bit RGBA
carries the transfer baked); the SDR overlay composites unscaled onto
an HDR10 surface (dim OSD); no vkSetHdrMetadataEXT yet.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs-site/content/docs/hyprland.md

@@ -34,9 +34,10 @@ See [Configuration](/docs/configuration) for the full reference.
 ## How it works
 
 - **Video** — the host runs `hyprctl output create headless PF-1` and applies a monitor rule for the
-  client's exact mode. Outputs are **named**, so there's no before/after diffing. Both config eras
-  are supported: `hyprctl keyword monitor …` (≤ 0.54) and the Lua `hyprctl eval 'hl.monitor{…}'`
-  (≥ 0.55), selected from `hyprctl version`.
+  client's exact mode. Outputs are **named**, so there's no before/after diffing. The rule uses
+  `hyprctl keyword monitor …` (the hyprlang config manager — the default on every release, 0.55
+  included) and falls back to the Lua `hyprctl eval 'hl.monitor{…}'` only if you've opted into the
+  Lua config manager. The host confirms the output actually adopted the mode before streaming.
 - **Capture** — it captures that output through the **xdg-desktop-portal-hyprland (xdph)** ScreenCast
   portal. To pick the output without a GUI on a headless host, the host writes a managed
   `~/.config/hypr/xdph.conf` pointing xdph's `custom_picker_binary` at a small shim that selects the