build(android): cfg-gate desktop-only Tauri surfaces for android target

Phase 1 of the Android same-repo target plan: make the workspace
compilable for `aarch64-linux-android` (and the other NDK ABIs) by
removing the desktop-only crate dependencies and command bodies from the
Android build. After this commit, `tauri android init` followed by
`cargo tauri android build` is structurally unblocked — the remaining
work is the SDK/NDK toolchain (off-sandbox), the Svelte single-window
refactor, and the Phase 3 MVP feature surface.

What's gated under `cfg(not(target_os = "android"))`:

- src-tauri/Cargo.toml: `tauri = { features = ["tray-icon"] }` is now
  declared in the desktop-only target block. The `global-shortcut`,
  `window-state`, and `autostart` plugins join it — none of the three
  support Android natively. The base `tauri = "2"` plus `dialog`,
  `opener`, and `notification` plugins remain unconditional because they
  do support Android.
- src-tauri/src/lib.rs: `mod tray` declaration, the matching
  `tray::setup(app)` call, the close-to-tray `WindowEvent::CloseRequested`
  handler, and the `.plugin(tauri_plugin_global_shortcut::*)` /
  `_autostart` / `_window_state` chain are all desktop-only. The
  builder is split with a single `#[cfg(not(target_os = "android"))]`
  branch that adds the desktop plugins on top of the universal base.
- src-tauri/src/commands/tts.rs: `tts_speak` previously had three
  `#[cfg(target_os = ...)]` branches but no fallback, so on Android the
  `spawned` binding was unbound and the function failed to compile.
  Mirrored the existing `paste.rs` not-implemented fallback. Same fix
  for `list_voices_impl`. Frontend will hide the Read Page Aloud button
  on Android via `isAndroid()`.
- src-tauri/src/commands/windows.rs: all four multi-window commands
  (`open_task_window`, `open_preview_window`, `close_preview_window`,
  `open_viewer_window`) get an Android stub that returns a clear
  "Multi-window is not supported on Android" error. Tauri on Android
  is single-Activity; the previously-secondary content (preview overlay,
  transcript viewer, task float) will live as routes inside the main
  window, gated by `isAndroid()` on the frontend.

What's *not* changed:
- Top-level `identifier` in tauri.conf.json stays `uk.co.corbel.kon`.
  The Phase 10b Kon → Corbie rename sweep will land
  `corbel.technology.corbie` as part of a coherent rebrand commit
  rather than fragmenting the rename across this branch.
- `bundle.android.minSdkVersion: 24` added so a future
  `tauri android init` knows to target Android 7.0+ (Vulkan available,
  scoped storage starts at 29 — we'll surface scoped-storage paths
  via Tauri's dialog plugin on Phase 3).
- `kon-hotkey` already exports a non-Linux stub; no changes needed.
- `commands/meeting.rs` still calls `process_watch::list_running_process_names()`
  which compiles on Android but returns an empty list (SELinux blocks
  /proc walk on API 24+). Frontend will hide the toggle on Android.

Verification: 91/91 tests still pass on the buildable-in-sandbox crates
(kon-storage 60, kon-core 16, kon-mcp 9, kon-hotkey 4, kon-cloud-providers
2). svelte-check 0/0 across 3957 files. The src-tauri crate itself can't
be compiled in this sandbox (no webkit2gtk); CI's desktop builders will
exercise the desktop branch, and Jake's Android-equipped dev box will
exercise the Android branch via `tauri android init`.

https://claude.ai/code/session_0189xUb6ie6t9qHkzatGZ9Rb

src-tauri/Cargo.toml

@@ -37,16 +37,13 @@ kon-cloud-providers = { path = "../crates/cloud-providers" }
 kon-hotkey = { path = "../crates/hotkey" }
 kon-llm = { path = "../crates/llm" }
 
-# Tauri
-tauri = { version = "2", features = ["tray-icon"] }
+# Tauri. The `tray-icon` feature, the global-shortcut/window-state/
+# autostart plugins are desktop-only — gated below under
+# cfg(not(target_os = "android")). The dialog, opener, and notification
+# plugins all support Android natively so live in the unconditional list.
+tauri = { version = "2" }
 tauri-plugin-opener = "2"
 tauri-plugin-dialog = "2"
-tauri-plugin-global-shortcut = "2"
-tauri-plugin-window-state = "2"
-# Phase 5 rituals: register Corbie as a login-time autostart entry.
-# Handles platform differences (.desktop file on Linux, LaunchAgents plist
-# on macOS, registry Run key on Windows) behind a single API.
-tauri-plugin-autostart = "2"
 # Phase 6 nudges: OS-native notifications via the frontend-owned nudge
 # bus. Permission-request flow happens on the JS side before the first
 # deliver_nudge call; Windows only delivers for installed apps.
@@ -79,6 +76,25 @@ uuid = { version = "1", features = ["v4"] }
 # pollute the workspace.
 tempfile = "3"
 
+# Desktop-only Tauri features and plugins. Each item below either fails
+# to compile against the Android NDK or is a structural no-op on a
+# single-window mobile app:
+#   - tray-icon: no system tray on mobile.
+#   - global-shortcut: mobile has no global hotkey API; the foreground
+#     notification with a record button is the Android replacement.
+#   - window-state: single-window, fullscreen, no per-window persistence.
+#   - autostart: mobile apps don't auto-start in the desktop sense; if
+#     we ever want a "boot completed" handler that's a separate Android
+#     intent receiver, not this plugin.
+[target.'cfg(not(target_os = "android"))'.dependencies]
+tauri = { version = "2", features = ["tray-icon"] }
+tauri-plugin-global-shortcut = "2"
+tauri-plugin-window-state = "2"
+# Phase 5 rituals: register Corbie as a login-time autostart entry.
+# Handles platform differences (.desktop file on Linux, LaunchAgents plist
+# on macOS, registry Run key on Windows) behind a single API.
+tauri-plugin-autostart = "2"
+
 [target.'cfg(target_os = "linux")'.dependencies]
 webkit2gtk = "2.0"
 # Needed for setting the preview overlay's WindowTypeHint to Utility via