feat(paste): auto-insert transcript at cursor via wtype/xdotool/ydotool/osascript/SendKeys

Adds an opt-in "auto-paste into focused window" toggle. When enabled, the
dictation pipeline sets the clipboard and then sends a Ctrl+V / Cmd+V
keystroke to whatever window currently has focus — the common case after a
global-hotkey dictation, since Kon's own window never stole focus.

Backend (src-tauri/src/commands/paste.rs) probes for a platform paste tool
and falls back cleanly:
- Linux Wayland: wtype > ydotool > xdotool
- Linux X11: xdotool > ydotool > wtype
- macOS: osascript System Events keystroke
- Windows: PowerShell WScript.Shell SendKeys

detect_paste_backends is a pure probe used by Settings to describe the
available backend next to the toggle (or nudge the user to install one).
paste_text always copies first, so auto-paste failure degrades to the
existing clipboard-only behaviour and surfaces a warn toast.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/pages/DictationPage.svelte

@@ -479,7 +479,22 @@
         replaceSegmentsWithCleanedText(cleanedTranscript);
       }
 
-      if (settings.autoCopy) {
+      if (settings.autoPaste) {
+        try {
+          const outcome = await invoke("paste_text", { text: transcript });
+          if (!outcome?.pasted && outcome?.message) {
+            toasts.warn(
+              "Auto-paste unavailable",
+              `${outcome.message}${outcome.copied ? ". Transcript is on your clipboard." : ""}`,
+            );
+          }
+        } catch (err) {
+          await navigator.clipboard
+            .writeText(transcript)
+            .catch(() => invoke("copy_to_clipboard", { text: transcript }).catch(() => {}));
+          toasts.warn("Auto-paste failed", String(err));
+        }
+      } else if (settings.autoCopy) {
         navigator.clipboard.writeText(transcript).catch(() => {
           invoke("copy_to_clipboard", { text: transcript }).catch(() => {});
         });