feat: GPUI desktop port foundation

- scene crate: full project/scene/element model, serde round-trip
  proven against the web SerializedProject shape
- transfer crate: .ocp zip container, cross-compat with web fflate
  archives proven in both directions
- storage crate: filesystem project store replacing IndexedDB,
  .ocp import/export
- media crate: ffmpeg-next 8 decoder (frames, audio, thumbnails,
  waveform summaries)
- playback crate: wall-clock anchored, frame-rounded playback clock
- gpu crate: native texture readback; compositor renders headless
  offscreen on Vulkan (spike test)
- flake devshell: rust toolchain, GPUI native deps, ffmpeg dev,
  bindgen clang args; GPUI hello-world builds
- port plan in notes/gpui-port.md

1 files changed, 57 insertions, 0 deletions

diff --git a/rust/crates/effect-defs/src/math.rs b/rust/crates/effect-defs/src/math.rs
new file mode 100644
index 00000000..dafc281e
--- /dev/null
+++ b/rust/crates/effect-defs/src/math.rs
@@ -0,0 +1,57 @@
+pub(crate) fn js_max(a: f64, b: f64) -> f64 {
+    if a.is_nan() || b.is_nan() { f64::NAN } else { a.max(b) }
+}
+
+pub(crate) fn js_min(a: f64, b: f64) -> f64 {
+    if a.is_nan() || b.is_nan() { f64::NAN } else { a.min(b) }
+}
+
+pub(crate) fn js_parse_float(value: &str) -> f64 {
+    let trimmed = value.trim_start();
+    let (sign, rest) = match trimmed.strip_prefix('-') {
+        Some(rest) => (-1.0, rest),
+        None => (1.0, trimmed.strip_prefix('+').unwrap_or(trimmed)),
+    };
+    if rest.starts_with("Infinity") {
+        return sign * f64::INFINITY;
+    }
+    let bytes = rest.as_bytes();
+    let mut end = 0;
+    let mut seen_digit = false;
+    let mut seen_dot = false;
+    while end < bytes.len() {
+        match bytes[end] {
+            b'0'..=b'9' => {
+                seen_digit = true;
+                end += 1;
+            }
+            b'.' if !seen_dot => {
+                seen_dot = true;
+                end += 1;
+            }
+            _ => break,
+        }
+    }
+    if !seen_digit {
+        return f64::NAN;
+    }
+    let mantissa_end = end;
+    if end < bytes.len() && (bytes[end] == b'e' || bytes[end] == b'E') {
+        let mut exponent_end = end + 1;
+        if exponent_end < bytes.len()
+            && (bytes[exponent_end] == b'+' || bytes[exponent_end] == b'-')
+        {
+            exponent_end += 1;
+        }
+        let digits_start = exponent_end;
+        while exponent_end < bytes.len() && bytes[exponent_end].is_ascii_digit() {
+            exponent_end += 1;
+        }
+        if exponent_end > digits_start {
+            end = exponent_end;
+        } else {
+            end = mantissa_end;
+        }
+    }
+    sign * rest[..end].parse::<f64>().unwrap_or(f64::NAN)
+}