feat: port domain crates to Rust (session 1 complete)

All green: cargo test --workspace (~300 tests, 0 failures).
- timeline (45): placement, resize/ripple, split, snap, retime,
  audio separation, scene helpers
- animation (73): bezier solver, channel sampling, keyframe ops,
  split/clamp/clone, param definitions
- commands (9): Command trait, BatchCommand, history, 19 concrete
  commands, freeze-frame port 1:1
- audio (22): audible collection, range mixing, mastering limiter,
  rms/peak buckets
- text (19): cosmic-text layout/measure/raster, backgrounds,
  decorations
- graphics (52): full CSS gradient parser, tiny-skia raster,
  4 shape definitions
- effect-defs (16): blur definition, registry, pass resolution
- mask-defs (19): all 9 mask renderers via tiny-skia
- renderer (6): node model + scene builder port
- desktop: GPUI projects screen wired to ProjectStore
- scene: factory (web defaults: v32, Main Track, 1920x1080, 30fps)

1 files changed, 166 insertions, 0 deletions

diff --git a/rust/crates/text/src/params.rs b/rust/crates/text/src/params.rs
new file mode 100644
index 00000000..bf2d7702
--- /dev/null
+++ b/rust/crates/text/src/params.rs
@@ -0,0 +1,166 @@
+use scene::params::{ParamValue, ParamValues};
+
+pub const MIN_FONT_SIZE: f64 = 5.0;
+pub const MAX_FONT_SIZE: f64 = 300.0;
+pub const DEFAULT_TEXT_COLOR: &str = "#000000";
+pub const FONT_SIZE_SCALE_REFERENCE: f64 = 90.0;
+pub const CORNER_RADIUS_MIN: f64 = 0.0;
+pub const CORNER_RADIUS_MAX: f64 = 100.0;
+pub const DEFAULT_LETTER_SPACING: f64 = 0.0;
+pub const DEFAULT_LINE_HEIGHT: f64 = 1.2;
+pub const DEFAULT_BACKGROUND_ENABLED: bool = false;
+pub const DEFAULT_BACKGROUND_COLOR: &str = "#000000";
+pub const DEFAULT_BACKGROUND_CORNER_RADIUS: f64 = 0.0;
+pub const DEFAULT_BACKGROUND_PADDING_X: f64 = 30.0;
+pub const DEFAULT_BACKGROUND_PADDING_Y: f64 = 42.0;
+pub const DEFAULT_BACKGROUND_OFFSET_X: f64 = 0.0;
+pub const DEFAULT_BACKGROUND_OFFSET_Y: f64 = 0.0;
+
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+pub enum TextAlign {
+    Left,
+    #[default]
+    Center,
+    Right,
+}
+
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+pub enum FontWeight {
+    #[default]
+    Normal,
+    Bold,
+}
+
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+pub enum FontStyle {
+    #[default]
+    Normal,
+    Italic,
+}
+
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+pub enum TextDecoration {
+    #[default]
+    None,
+    Underline,
+    LineThrough,
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub struct TextLayoutParams {
+    pub content: String,
+    pub font_size: f64,
+    pub font_family: String,
+    pub font_weight: FontWeight,
+    pub font_style: FontStyle,
+    pub text_align: TextAlign,
+    pub text_decoration: TextDecoration,
+    pub letter_spacing: f64,
+    pub line_height: f64,
+}
+
+impl Default for TextLayoutParams {
+    fn default() -> Self {
+        Self {
+            content: "Default text".to_string(),
+            font_size: 15.0,
+            font_family: "Arial".to_string(),
+            font_weight: FontWeight::Normal,
+            font_style: FontStyle::Normal,
+            text_align: TextAlign::Center,
+            text_decoration: TextDecoration::None,
+            letter_spacing: DEFAULT_LETTER_SPACING,
+            line_height: DEFAULT_LINE_HEIGHT,
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub struct TextBackground {
+    pub enabled: bool,
+    pub color: String,
+    pub corner_radius: f64,
+    pub padding_x: f64,
+    pub padding_y: f64,
+    pub offset_x: f64,
+    pub offset_y: f64,
+}
+
+impl Default for TextBackground {
+    fn default() -> Self {
+        Self {
+            enabled: DEFAULT_BACKGROUND_ENABLED,
+            color: DEFAULT_BACKGROUND_COLOR.to_string(),
+            corner_radius: DEFAULT_BACKGROUND_CORNER_RADIUS,
+            padding_x: DEFAULT_BACKGROUND_PADDING_X,
+            padding_y: DEFAULT_BACKGROUND_PADDING_Y,
+            offset_x: DEFAULT_BACKGROUND_OFFSET_X,
+            offset_y: DEFAULT_BACKGROUND_OFFSET_Y,
+        }
+    }
+}
+
+pub fn text_layout_params_from(params: &ParamValues) -> TextLayoutParams {
+    TextLayoutParams {
+        content: string_param(params, "content", "Default text"),
+        font_size: number_param(params, "fontSize", 15.0),
+        font_family: string_param(params, "fontFamily", "Arial"),
+        font_weight: match string_param(params, "fontWeight", "normal").as_str() {
+            "bold" => FontWeight::Bold,
+            _ => FontWeight::Normal,
+        },
+        font_style: match string_param(params, "fontStyle", "normal").as_str() {
+            "italic" => FontStyle::Italic,
+            _ => FontStyle::Normal,
+        },
+        text_align: match string_param(params, "textAlign", "center").as_str() {
+            "left" => TextAlign::Left,
+            "right" => TextAlign::Right,
+            _ => TextAlign::Center,
+        },
+        text_decoration: match string_param(params, "textDecoration", "none").as_str() {
+            "underline" => TextDecoration::Underline,
+            "line-through" => TextDecoration::LineThrough,
+            _ => TextDecoration::None,
+        },
+        letter_spacing: number_param(params, "letterSpacing", DEFAULT_LETTER_SPACING),
+        line_height: number_param(params, "lineHeight", DEFAULT_LINE_HEIGHT),
+    }
+}
+
+pub fn text_background_from(params: &ParamValues) -> TextBackground {
+    TextBackground {
+        enabled: bool_param(params, "background.enabled", DEFAULT_BACKGROUND_ENABLED),
+        color: string_param(params, "background.color", DEFAULT_BACKGROUND_COLOR),
+        corner_radius: number_param(
+            params,
+            "background.cornerRadius",
+            DEFAULT_BACKGROUND_CORNER_RADIUS,
+        ),
+        padding_x: number_param(params, "background.paddingX", DEFAULT_BACKGROUND_PADDING_X),
+        padding_y: number_param(params, "background.paddingY", DEFAULT_BACKGROUND_PADDING_Y),
+        offset_x: number_param(params, "background.offsetX", DEFAULT_BACKGROUND_OFFSET_X),
+        offset_y: number_param(params, "background.offsetY", DEFAULT_BACKGROUND_OFFSET_Y),
+    }
+}
+
+fn string_param(params: &ParamValues, key: &str, fallback: &str) -> String {
+    match params.get(key) {
+        Some(ParamValue::String(value)) => value.clone(),
+        _ => fallback.to_string(),
+    }
+}
+
+fn number_param(params: &ParamValues, key: &str, fallback: f64) -> f64 {
+    match params.get(key) {
+        Some(ParamValue::Number(value)) => *value,
+        _ => fallback,
+    }
+}
+
+fn bool_param(params: &ParamValues, key: &str, fallback: bool) -> bool {
+    match params.get(key) {
+        Some(ParamValue::Bool(value)) => *value,
+        _ => fallback,
+    }
+}