feat: Sprint 17 -- workspace breadcrumbs, slash commands, send key setting

Track A: Workspace breadcrumb navigation
- Breadcrumb path bar with clickable segments when inside subdirectories
- Up button in panel header for parent directory navigation
- S.currentDir state tracking; file ops stay in current directory
- New file/folder creation respects current subdirectory

Track B: Slash commands foundation
- New commands.js module (7th JS module) with command registry and parser
- Built-in commands: /help, /clear, /model, /workspace, /new
- Autocomplete dropdown on / input with arrow/tab/enter/escape navigation
- Unrecognized commands pass through to agent normally

Track C: Send key setting (closes #26)
- send_key added to settings defaults in api/config.py
- Settings panel dropdown: Enter (default) vs Ctrl/Cmd+Enter
- Keydown handler rewritten for autocomplete + send key preference
- Setting loaded on boot, persisted to settings.json

5 new tests, 242 total (219 passing, 22 pre-existing failures, 0 regressions).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

static/workspace.js

@@ -9,11 +9,19 @@ async function api(path,opts={}){
 async function loadDir(path){
   if(!S.session)return;
   try{
+    S.currentDir=path||'.';
     const data=await api(`/api/list?session_id=${encodeURIComponent(S.session.session_id)}&path=${encodeURIComponent(path)}`);
-    S.entries=data.entries||[];renderFileTree();
+    S.entries=data.entries||[];renderBreadcrumb();renderFileTree();
   }catch(e){console.warn('loadDir',e);}
 }
 
+function navigateUp(){
+  if(!S.session||S.currentDir==='.')return;
+  const parts=S.currentDir.split('/');
+  parts.pop();
+  loadDir(parts.length?parts.join('/'):'.');
+}
+
 // File extension sets for preview routing (must match server-side sets)
 const IMAGE_EXTS  = new Set(['.png','.jpg','.jpeg','.gif','.svg','.webp','.ico','.bmp']);
 const MD_EXTS     = new Set(['.md','.markdown','.mdown']);