Add Fensalir program control surface

docs/program-control-surface.md

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+# Program Control Surface
+
+Mimir now exposes a compact Fensalir-hosted program panel for final presentation
+intent.
+
+Authority map:
+
+- Owner: `MimirPresentationControlState` owns operator intent for program video,
+  audio mix, and global color preset.
+- Inputs: runtime rolling buffers, aligned audio lanes, LUT preset selection,
+  feed visibility, feed opacity, stem mute/solo, and stem gain.
+- Outputs: filtered video surface intents, Faust/native DSP gain controls,
+  sample gain applied before Fensalir streaming DSP, and a postprocess control
+  snapshot.
+- Derived state: feed lists are derived from active rolling buffers. LUT preset
+  exposure and bloom are currently mapped into `GraphicsSettings`.
+- Forbidden writers: OBS, bridge endpoints, debug readouts, and network arrival
+  timestamps must not choose program composition.
+- Shared paths: local cameras, Raven display capture, and future network video
+  feeds all enter rolling buffers first, then the presentation state decides
+  whether they contribute to production surface intent.
+- Deletion line: direct compositor shortcuts outside Fensalir FieldEvidence and
+  audio DSP are diagnostic only.
+
+The current UI lives in the `Mimir Program` panel:
+
+- `Video`: select feed, visible, solo, opacity, layer ordering.
+- `Audio`: select stem/source, mute, solo, gain.
+- `Color`: LUT preset and LUT strength.
+
+The shader-side LUT path is explicit state, not finished renderer authority yet.
+`MimirLookupTablePreset` carries `LutPath`, strength, contrast, saturation,
+temperature, and tint so Fensalir can consume the same contract when the global
+post shader grows real LUT sampling. Until that renderer cut lands, Mimir maps
+the preset exposure and bloom values into existing Fensalir `GraphicsSettings`.
+
+Smoke proof:
+
+```powershell
+dotnet run --project .\src\Mimir.BufferSmoke\Mimir.BufferSmoke.csproj -- --presentation-control-smoke
+```
+