feat: studio-theme-solarized v0.1.0 — skeleton

First Studio plugin in the new `studio.*` capability namespace.
SKELETON — does not yet compile.

Why ship the skeleton now:

  * Pins Ethan Schoonover's Solarized palette as two const
    Material 3 ColorScheme arrays so the in-tree reference
    doesn't bike-shed at SDK-integration time.
  * Gives the future fai-studio-plugin-sdk author a concrete
    consumer to validate the generated `#[plugin(theme)]`
    macro output against.
  * Validates that the WIT in fai/platform parses by being a
    real crate that references it.

What it does NOT yet do:

  * Compile. The `fai-studio-plugin-sdk` dependency it points
    at doesn't exist. Tracked in
    `fai/platform/docs/advanced/studio-plugin-sdk.md`.
  * Plug into Studio. The plugin-host module that would
    discover and invoke this component lives in the same
    deferred-Phase-1 work.

What it ships:

  * module.yaml declaring `provides: studio.theme.solarized`
    and `studio_extension.hooks: [theme]`.
  * Cargo.toml with the future SDK dependency commented out,
    crate-type=cdylib, component metadata.
  * src/lib.rs with both Solarized colour palettes
    (SOLARIZED_LIGHT and SOLARIZED_DARK), 14 ARGB tokens
    each in Material 3 order, plus the future `#[plugin]`
    function body commented out and two sanity tests on the
    palette constants.
  * README.md explaining the status and the steps to finish
    the plugin once the SDK ships.

Signed-off-by: flemming-it <sf@flemming.it>

src/lib.rs

@@ -0,0 +1,106 @@
+//! `studio.theme.solarized` — first Studio plugin.
+//!
+//! Ships Ethan Schoonover's Solarized palette as a Material 3
+//! ColorScheme pair (light + dark).
+//!
+//! SKELETON: this file does not yet compile. The
+//! `#[plugin(theme)]` macro and the `studio_plugin` runtime live
+//! in `fai-studio-plugin-sdk`, which is documented in
+//! `docs/advanced/studio-plugin-sdk.md` but not yet implemented.
+//! Once the SDK ships, switching the file from skeleton to
+//! buildable is a matter of uncommenting the dependency in
+//! Cargo.toml and the use-line below.
+//!
+//! Why ship the skeleton now: pins the palette so the in-tree
+//! reference plugin doesn't bike-shed at SDK-integration time,
+//! and gives the SDK author a concrete consumer to validate
+//! their generated macro output against.
+
+#![allow(dead_code, unused_imports)]
+
+// use fai_studio_plugin_sdk::{plugin, theme, ColorScheme};
+
+/// 14 ARGB tokens, Material 3 order:
+///   primary, on_primary, secondary, on_secondary,
+///   tertiary, on_tertiary, error, on_error,
+///   surface, on_surface, surface_variant, on_surface_variant,
+///   outline, outline_variant.
+///
+/// Studio merges any missing slot (we send all 14, so none) with
+/// its built-in fallback before applying.
+const SOLARIZED_LIGHT: [u32; 14] = [
+    0xFF268BD2, // primary           — solarized blue
+    0xFFFDF6E3, // on_primary        — base3
+    0xFF2AA198, // secondary         — solarized cyan
+    0xFFFDF6E3, // on_secondary      — base3
+    0xFFB58900, // tertiary          — solarized yellow
+    0xFF002B36, // on_tertiary       — base03
+    0xFFDC322F, // error             — solarized red
+    0xFFFDF6E3, // on_error          — base3
+    0xFFFDF6E3, // surface           — base3
+    0xFF073642, // on_surface        — base02
+    0xFFEEE8D5, // surface_variant   — base2
+    0xFF586E75, // on_surface_variant — base01
+    0xFF93A1A1, // outline           — base1
+    0xFFEEE8D5, // outline_variant   — base2
+];
+
+const SOLARIZED_DARK: [u32; 14] = [
+    0xFF268BD2, // primary           — solarized blue
+    0xFF002B36, // on_primary        — base03
+    0xFF2AA198, // secondary         — solarized cyan
+    0xFF002B36, // on_secondary      — base03
+    0xFFB58900, // tertiary          — solarized yellow
+    0xFF002B36, // on_tertiary       — base03
+    0xFFDC322F, // error             — solarized red
+    0xFF002B36, // on_error          — base03
+    0xFF002B36, // surface           — base03
+    0xFF93A1A1, // on_surface        — base1
+    0xFF073642, // surface_variant   — base02
+    0xFF839496, // on_surface_variant — base0
+    0xFF586E75, // outline           — base01
+    0xFF073642, // outline_variant   — base02
+];
+
+// ─────────────────────────────────────────────────────────────
+// Forward-reference: this is the shape the SDK will generate
+// from `#[plugin(theme)]`. Once the SDK exists, the body collapses
+// to a return of `Ok(ColorScheme { brightness, tokens: … })`.
+// ─────────────────────────────────────────────────────────────
+//
+// #[plugin(theme)]
+// fn theme_for(brightness: &str) -> theme::Result {
+//     let tokens = match brightness {
+//         "light" => SOLARIZED_LIGHT.to_vec(),
+//         "dark"  => SOLARIZED_DARK.to_vec(),
+//         other => {
+//             return Err(theme::Error::declined(format!(
+//                 "solarized has no scheme for brightness '{other}'",
+//             )))
+//         }
+//     };
+//     Ok(ColorScheme {
+//         brightness: brightness.to_string(),
+//         tokens,
+//     })
+// }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn palette_has_14_tokens() {
+        assert_eq!(SOLARIZED_LIGHT.len(), 14);
+        assert_eq!(SOLARIZED_DARK.len(), 14);
+    }
+
+    #[test]
+    fn solarized_blue_is_the_primary_in_both_modes() {
+        // Ethan Schoonover's blue is the brand colour of
+        // Solarized. Sanity-check we kept it as the primary in
+        // both schemes.
+        assert_eq!(SOLARIZED_LIGHT[0], 0xFF268BD2);
+        assert_eq!(SOLARIZED_DARK[0], 0xFF268BD2);
+    }
+}