fix(electrobun): address all 20 Codex review findings

CRITICAL:
- PTY leak: Terminal.svelte now calls pty.close on destroy, not just unsubscribe
- Agent session cleanup: clearSession() removes done/error sessions, backend
  deletes after 60s grace period

HIGH:
- Clone branch passthrough: user's branch name flows through callback
- Circular imports: extracted rpc.ts singleton, broke main.ts ↔ App.svelte cycle
- Settings wired to runtime: Terminal reads cursor/scrollback from settings
- Security disclaimer: added "prototype — not system keyring" notice
- ThemeEditor: fixed basePalette → initialPalette reference

MEDIUM:
- Clone race: UUID suffix instead of count-based index
- Silent failures: structured error returns from PTY handlers
- WebKitGTK mount: only current + previous group mounted
- Debug listeners: gated behind DEBUG, cleanup on destroy
- NDJSON residual buffer parsed on process exit
- Codex adapter: deduplicated tool_call/tool_result
- extraEnv: rejects CLAUDE*/CODEX*/OLLAMA* keys
- settings-db: runMigrations() with version tracking
- active_group: persisted via settings.set

LOW:
- Removed dead demo code, unused variables
- color-mix() fallbacks added

ui-electrobun/src/mainview/Terminal.svelte

@@ -4,7 +4,7 @@
   import { CanvasAddon } from '@xterm/addon-canvas';
   import { FitAddon } from '@xterm/addon-fit';
   import { ImageAddon } from '@xterm/addon-image';
-  import { electrobun } from './main.ts';
+  import { appRpc } from './rpc.ts';
   import { fontStore } from './font-store.svelte.ts';
   import { themeStore } from './theme-store.svelte.ts';
   import { getXtermTheme } from './themes.ts';
@@ -22,6 +22,7 @@
   let fitAddon: FitAddon;
   let unsubFont: (() => void) | null = null;
   let ro: ResizeObserver | null = null;
+  let destroyed = false;
 
   /** Decode a base64 string from the daemon into a Uint8Array. */
   function decodeBase64(b64: string): Uint8Array {
@@ -60,20 +61,41 @@
     term.open(termEl);
     fitAddon.fit();
 
+    // ── Read cursor/scrollback settings ─────────────────────────────────
+
+    void (async () => {
+      try {
+        const { settings } = await appRpc.request['settings.getAll']({});
+        if (settings['cursor_style']) {
+          const style = settings['cursor_style'];
+          if (style === 'block' || style === 'underline' || style === 'bar') {
+            term.options.cursorStyle = style;
+          }
+        }
+        if (settings['cursor_blink'] === 'false') {
+          term.options.cursorBlink = false;
+        }
+        if (settings['scrollback']) {
+          const sb = parseInt(settings['scrollback'], 10);
+          if (!isNaN(sb) && sb >= 0) term.options.scrollback = sb;
+        }
+      } catch { /* non-critical — use defaults */ }
+    })();
+
     // ── Subscribe to terminal font changes ─────────────────────────────────
 
     unsubFont = fontStore.onTermFontChange((family: string, size: number) => {
       term.options.fontFamily = family || 'JetBrains Mono, Fira Code, monospace';
       term.options.fontSize   = size;
       fitAddon.fit();
-      electrobun.rpc?.request['pty.resize']({ sessionId, cols: term.cols, rows: term.rows }).catch(() => {});
+      appRpc.request['pty.resize']({ sessionId, cols: term.cols, rows: term.rows }).catch(() => {});
     });
 
     // ── Connect to PTY daemon (fire-and-forget from onMount) ───────────────
 
     void (async () => {
       const { cols, rows } = term;
-      const result = await electrobun.rpc?.request['pty.create']({ sessionId, cols, rows, cwd });
+      const result = await appRpc.request['pty.create']({ sessionId, cols, rows, cwd });
       if (!result?.ok) {
         term.writeln(`\x1b[31m[agor] Failed to connect to PTY daemon: ${result?.error ?? 'unknown error'}\x1b[0m`);
         term.writeln('\x1b[33m[agor] Is agor-ptyd running? Start it with: agor-ptyd\x1b[0m');
@@ -82,20 +104,22 @@
 
     // ── Receive output from daemon ─────────────────────────────────────────
 
-    electrobun.rpc?.addMessageListener('pty.output', ({ sessionId: sid, data }: { sessionId: string; data: string }) => {
-      if (sid !== sessionId) return;
+    const outputHandler = ({ sessionId: sid, data }: { sessionId: string; data: string }) => {
+      if (destroyed || sid !== sessionId) return;
       term.write(decodeBase64(data));
-    });
+    };
+    appRpc.addMessageListener('pty.output', outputHandler);
 
-    electrobun.rpc?.addMessageListener('pty.closed', ({ sessionId: sid, exitCode }: { sessionId: string; exitCode: number | null }) => {
-      if (sid !== sessionId) return;
+    const closedHandler = ({ sessionId: sid, exitCode }: { sessionId: string; exitCode: number | null }) => {
+      if (destroyed || sid !== sessionId) return;
       term.writeln(`\r\n\x1b[90m[Process exited${exitCode !== null ? ` with code ${exitCode}` : ''}]\x1b[0m`);
-    });
+    };
+    appRpc.addMessageListener('pty.closed', closedHandler);
 
     // ── Send user input to daemon ──────────────────────────────────────────
 
     term.onData((data: string) => {
-      electrobun.rpc?.request['pty.write']({ sessionId, data }).catch((err: unknown) => {
+      appRpc.request['pty.write']({ sessionId, data }).catch((err: unknown) => {
         console.error('[pty.write] error:', err);
       });
     });
@@ -103,7 +127,7 @@
     // ── Sync resize events to daemon ───────────────────────────────────────
 
     term.onResize(({ cols: c, rows: r }) => {
-      electrobun.rpc?.request['pty.resize']({ sessionId, cols: c, rows: r }).catch(() => {});
+      appRpc.request['pty.resize']({ sessionId, cols: c, rows: r }).catch(() => {});
     });
 
     ro = new ResizeObserver(() => { fitAddon.fit(); });
@@ -111,9 +135,11 @@
   });
 
   onDestroy(() => {
+    destroyed = true;
     unsubFont?.();
     ro?.disconnect();
-    electrobun.rpc?.request['pty.unsubscribe']({ sessionId }).catch(() => {});
+    // Fix #1: Close the PTY session (not just unsubscribe) to prevent session leak
+    appRpc.request['pty.close']({ sessionId }).catch(() => {});
     term?.dispose();
   });
 </script>