fix: forward browser terminal pastes as bracketed input

- Track application bracketed-paste mode from terminal output.
- Capture browser and mobile clipboard pastes only while that mode is enabled,
  normalizing line endings and sending a single BPM-framed input event.
- Remove the synchronous output decoding and console diagnostics that could
  stall terminal rendering under output load.
- Keep the terminal's zero-scrollback configuration and resolve existing
  no-case-declarations lint blockers in terminal keyboard shortcuts.

Quality gates: npm run typecheck, npm run lint

apps/web/src/hooks/use-terminal-page.ts

@@ -169,6 +169,10 @@ export const useTerminalPage = () => {
       const isAltShift = e.altKey && e.shiftKey && !e.ctrlKey && !e.metaKey;
       if (!isAltShift) return;
 
+      const activeSessionIndex = activeSessionId
+        ? sessions.findIndex((session) => session.id === activeSessionId)
+        : -1;
+
       switch (e.key.toLowerCase()) {
         case "n":
           e.preventDefault();
@@ -187,17 +191,14 @@ export const useTerminalPage = () => {
           break;
         case "arrowleft":
           e.preventDefault();
-          if (activeSessionId) {
-            const idx = sessions.findIndex((s) => s.id === activeSessionId);
-            if (idx > 0) setActiveSessionId(sessions[idx - 1].id);
+          if (activeSessionIndex > 0) {
+            setActiveSessionId(sessions[activeSessionIndex - 1].id);
           }
           break;
         case "arrowright":
           e.preventDefault();
-          if (activeSessionId) {
-            const idx = sessions.findIndex((s) => s.id === activeSessionId);
-            if (idx < sessions.length - 1)
-              setActiveSessionId(sessions[idx + 1].id);
+          if (activeSessionIndex >= 0 && activeSessionIndex < sessions.length - 1) {
+            setActiveSessionId(sessions[activeSessionIndex + 1].id);
           }
           break;
         case "r":
@@ -208,6 +209,8 @@ export const useTerminalPage = () => {
           e.preventDefault();
           setIsFullscreen((prev) => !prev);
           break;
+        default:
+          break;
       }
     };