feat(electrobun): add xterm.js terminal with image addon (Sixel/iTerm2)

- Terminal.svelte component with @xterm/xterm + Canvas + Fit + Image addons
- Catppuccin Mocha terminal theme matching main app
- Sixel, iTerm2 inline image protocol support via xterm-addon-image
- ResizeObserver for responsive terminal sizing
- Demo cargo test output in terminal section below agent messages

ui-electrobun/src/mainview/Terminal.svelte

@@ -0,0 +1,97 @@
+<script lang="ts">
+  import { onMount, onDestroy } from 'svelte';
+  import { Terminal } from '@xterm/xterm';
+  import { CanvasAddon } from '@xterm/addon-canvas';
+  import { FitAddon } from '@xterm/addon-fit';
+  import { ImageAddon } from '@xterm/addon-image';
+
+  // Catppuccin Mocha terminal theme
+  const THEME = {
+    background: '#1e1e2e',
+    foreground: '#cdd6f4',
+    cursor: '#f5e0dc',
+    cursorAccent: '#1e1e2e',
+    selectionBackground: '#585b7066',
+    black: '#45475a',
+    red: '#f38ba8',
+    green: '#a6e3a1',
+    yellow: '#f9e2af',
+    blue: '#89b4fa',
+    magenta: '#f5c2e7',
+    cyan: '#94e2d5',
+    white: '#bac2de',
+    brightBlack: '#585b70',
+    brightRed: '#f38ba8',
+    brightGreen: '#a6e3a1',
+    brightYellow: '#f9e2af',
+    brightBlue: '#89b4fa',
+    brightMagenta: '#f5c2e7',
+    brightCyan: '#94e2d5',
+    brightWhite: '#a6adc8',
+  };
+
+  let termEl: HTMLDivElement;
+  let term: Terminal;
+  let fitAddon: FitAddon;
+
+  onMount(() => {
+    term = new Terminal({
+      theme: THEME,
+      fontFamily: "'JetBrains Mono', 'Fira Code', monospace",
+      fontSize: 13,
+      cursorBlink: true,
+      allowProposedApi: true,
+      scrollback: 5000,
+    });
+
+    fitAddon = new FitAddon();
+    term.loadAddon(fitAddon);
+    term.loadAddon(new CanvasAddon());
+
+    // Image addon — enables Sixel, iTerm2, and Kitty inline image protocols
+    term.loadAddon(new ImageAddon({
+      enableSizeReports: true,
+      sixelSupport: true,
+      sixelScrolling: true,
+      sixelPaletteLimit: 4096,
+      showPlaceholder: true,
+    }));
+
+    term.open(termEl);
+    fitAddon.fit();
+
+    // Demo content with ANSI colors
+    term.writeln('\x1b[1;34m~/code/ai/agent-orchestrator\x1b[0m \x1b[32m$\x1b[0m cargo test --workspace');
+    term.writeln('    \x1b[1;32mCompiling\x1b[0m agor-core v0.1.0');
+    term.writeln('    \x1b[1;32mCompiling\x1b[0m agor-gpui v0.1.0');
+    term.writeln('     \x1b[1;32mRunning\x1b[0m tests/unit.rs');
+    term.writeln('test result: ok. \x1b[32m47 passed\x1b[0m; 0 failed');
+    term.writeln('');
+    term.writeln('\x1b[1;34m~/code/ai/agent-orchestrator\x1b[0m \x1b[32m$\x1b[0m \x1b[5m▊\x1b[0m');
+
+    // Resize on window resize
+    const ro = new ResizeObserver(() => fitAddon.fit());
+    ro.observe(termEl);
+
+    return () => ro.disconnect();
+  });
+
+  onDestroy(() => {
+    term?.dispose();
+  });
+</script>
+
+<div class="terminal-container" bind:this={termEl}></div>
+
+<style>
+  .terminal-container {
+    width: 100%;
+    height: 100%;
+    min-height: 10rem;
+  }
+
+  /* xterm.js base styles */
+  :global(.xterm) {
+    padding: 0.5rem;
+  }
+</style>