feat(electrobun): file management — CodeMirror editor, PDF viewer, CSV table, real file I/O

- CodeEditor: CodeMirror 6 with Catppuccin theme, 15+ languages, Ctrl+S save,
  dirty tracking, save-on-blur
- PdfViewer: pdfjs-dist canvas rendering, zoom 0.5-3x, HiDPI, lazy page load
- CsvTable: RFC 4180 parser, delimiter auto-detect, sortable columns, sticky header
- FileBrowser: real filesystem via files.list/read/write RPC, lazy dir loading,
  file type routing (code→editor, pdf→viewer, csv→table, images→display)
- 10MB size gate, binary detection, base64 encoding for non-text files

ui-electrobun/src/mainview/ProjectCard.svelte

@@ -3,12 +3,15 @@
   import TerminalTabs from './TerminalTabs.svelte';
   import FileBrowser from './FileBrowser.svelte';
   import MemoryTab from './MemoryTab.svelte';
+  import CommsTab from './CommsTab.svelte';
+  import TaskBoardTab from './TaskBoardTab.svelte';
   import {
     startAgent, stopAgent, sendPrompt, getSession, hasSession,
+    loadLastSession,
     type AgentStatus, type AgentMessage,
   } from './agent-store.svelte.ts';
 
-  type ProjectTab = 'model' | 'docs' | 'context' | 'files' | 'ssh' | 'memory';
+  type ProjectTab = 'model' | 'docs' | 'context' | 'files' | 'ssh' | 'memory' | 'comms' | 'tasks';
 
   interface Props {
     id: string;
@@ -29,6 +32,8 @@
     clonesAtMax?: boolean;
     /** Callback when user requests cloning (receives projectId and branch name). */
     onClone?: (projectId: string, branch: string) => void;
+    /** Group ID for btmsg/bttask context. */
+    groupId?: string;
   }
 
   let {
@@ -315,7 +320,7 @@
         role="tabpanel"
         aria-label="Files"
       >
-        <FileBrowser />
+        <FileBrowser {cwd} />
       </div>
     {/if}