feat(desktop): embed BoosAPI Desktop client as a subproject

Vendor the rebranded BoosAPI Desktop client (Tauri + Vue) into metapi as
a monorepo subdirectory under desktop/. Source only — node_modules,
dist, Cargo target and the upstream .git history are excluded.

desktop/ keeps its own independent Cargo workspace (desktop/src-tauri
with crates/*); it is not part of the backend boosapi crate, so a
`cargo check` at the metapi root still compiles only the backend. Build
the desktop app from desktop/src-tauri per desktop/README.md.

Note: app icons are still placeholder assets pending the final BoosAPI
logo. The updater signing keys live outside the repo and are not
included.

desktop/libs/markstream-vue/themes/opencode-ai.css

@@ -0,0 +1,59 @@
+/**
+ * markstream-vue theme: opencode-ai
+ * Auto-generated by scripts/theme-gen/cli.mjs
+ */
+
+/* ── Shared ── */
+.markstream-vue[data-theme="opencode-ai"] {
+  --ms-font-mono: "Berkeley Mono", "IBM Plex Mono", ui-monospace, SFMono-Regular, Menlo, monospace;
+  --ms-radius: 0.25rem;
+}
+
+/* ── Light ── */
+.markstream-vue[data-theme="opencode-ai"] {
+  --ms-background: 0 0% 98.4%;
+  --ms-foreground: 0 25.4% 11.6%;
+  --ms-muted: 0 0% 94.4%;
+  --ms-muted-foreground: 0 16.5% 42%;
+  --ms-secondary: 0 0% 95.4%;
+  --ms-secondary-foreground: 0 25.4% 21.6%;
+  --ms-accent: 351.1 6% 95.5%;
+  --ms-accent-foreground: 0 25.4% 16.6%;
+  --ms-primary: 211.3 100% 50%;
+  --ms-primary-foreground: 0 0% 0%;
+  --ms-destructive: 0 84.2% 60.2%;
+  --ms-destructive-foreground: 0 0% 0%;
+  --ms-border: 0 2.5% 57.7%;
+  --ms-ring: 0 25.4% 11.6%;
+  --ms-popover: 0 0% 98.4%;
+  --ms-popover-foreground: 0 25.4% 11.6%;
+  --ms-link: 206.3 100% 38%;
+}
+
+/* ── Dark ── */
+.dark .markstream-vue[data-theme="opencode-ai"],
+.markstream-vue[data-theme="opencode-ai"].dark {
+  --ms-background: 0 4.9% 12%;
+  --ms-foreground: 0 20% 99%;
+  --ms-muted: 0 4.9% 20%;
+  --ms-muted-foreground: 0 1% 60%;
+  --ms-secondary: 0 4.3% 18%;
+  --ms-secondary-foreground: 0 20% 89%;
+  --ms-accent: 345.1 14.4% 15.8%;
+  --ms-accent-foreground: 0 20% 94%;
+  --ms-primary: 211.3 100% 50%;
+  --ms-primary-foreground: 0 0% 100%;
+  --ms-destructive: 3.2 100% 59.4%;
+  --ms-destructive-foreground: 0 0% 0%;
+  --ms-border: 0 6.7% 43.4%;
+  --ms-ring: 0 20% 99%;
+  --ms-popover: 0 4.9% 12%;
+  --ms-popover-foreground: 0 20% 99%;
+  --ms-info: 211.3 100% 50%;
+  --ms-info-foreground: 0 0% 0%;
+  --ms-success: 134.9 63.6% 50.4%;
+  --ms-success-foreground: 0 0% 0%;
+  --ms-warning: 36.5 100% 52%;
+  --ms-warning-foreground: 0 0% 0%;
+  --ms-link: 221.3 100% 68%;
+}