feat: workspace git detection with branch/status badge

When the workspace root is a git repo, a badge in the panel header
shows the current branch name, dirty file count, and ahead/behind
status. Updates on every root directory load.

Backend:
- git_info_for_workspace() in api/workspace.py runs lightweight git
  commands (rev-parse, status --porcelain, rev-list) with 3s timeout
- New GET /api/git-info endpoint returns branch, dirty count, modified,
  untracked, ahead, behind

Frontend:
- _refreshGitBadge() in workspace.js fetches git info on root load
- Git badge element in panel header shows branch + status
- Badge turns gold when workspace has uncommitted changes

Inspired by PR #75 (@MartinNielsenDev).

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

static/index.html

@@ -278,6 +278,7 @@
     <div class="resize-handle" id="rightpanelResize"></div>
     <div class="panel-header">
       <span>Workspace</span>
+      <span class="git-badge" id="gitBadge" style="display:none"></span>
       <div class="panel-actions">
         <button class="panel-icon-btn" id="btnUpDir" title="Parent directory" onclick="navigateUp()" style="display:none">&#8593;</button>
         <button class="panel-icon-btn" id="btnNewFile" title="New file" onclick="promptNewFile()">&#43;</button>

static/style.css

@@ -204,6 +204,8 @@
   .upload-bar{height:100%;background:linear-gradient(90deg,var(--blue),#a0d0ff);width:0%;transition:width .3s ease;}
   .rightpanel{width:300px;background:var(--sidebar);border-left:1px solid rgba(255,255,255,.06);display:flex;flex-direction:column;overflow:hidden;flex-shrink:0;}
   .panel-header{padding:12px 16px;border-bottom:1px solid var(--border);font-size:11px;font-weight:600;color:var(--muted);text-transform:uppercase;letter-spacing:.1em;display:flex;align-items:center;justify-content:space-between;}
+  .git-badge{font-size:9px;font-weight:600;color:var(--muted);background:rgba(255,255,255,.06);padding:2px 7px;border-radius:4px;letter-spacing:.02em;margin-left:auto;margin-right:4px;white-space:nowrap;font-family:'SF Mono',ui-monospace,monospace;}
+  .git-badge.dirty{color:var(--gold);background:rgba(201,168,76,.1);}
   .panel-actions{display:flex;gap:4px;}
   .panel-icon-btn{width:24px;height:24px;background:none;border:none;color:var(--muted);cursor:pointer;border-radius:5px;font-size:13px;display:flex;align-items:center;justify-content:center;transition:all .15s;}
   .panel-icon-btn:hover{background:rgba(255,255,255,.08);color:var(--text);}

static/workspace.js

@@ -59,9 +59,32 @@ async function loadDir(path){
         clearPreview();
       }
     }
+    // Fetch git info for workspace root (non-blocking)
+    if(!path||path==='.') _refreshGitBadge();
   }catch(e){console.warn('loadDir',e);}
 }
 
+async function _refreshGitBadge(){
+  const badge=$('gitBadge');
+  if(!badge||!S.session)return;
+  try{
+    const data=await api(`/api/git-info?session_id=${encodeURIComponent(S.session.session_id)}`);
+    if(data.git&&data.git.is_git){
+      const g=data.git;
+      let text=g.branch||'git';
+      if(g.dirty>0) text+=` \u00b7 ${g.dirty}\u2206`; // middot + delta
+      if(g.behind>0) text+=` \u2193${g.behind}`;
+      if(g.ahead>0) text+=` \u2191${g.ahead}`;
+      badge.textContent=text;
+      badge.className='git-badge'+(g.dirty>0?' dirty':'');
+      badge.style.display='';
+    } else {
+      badge.style.display='none';
+      badge.textContent='';
+    }
+  }catch(e){badge.style.display='none';}
+}
+
 function navigateUp(){
   if(!S.session||S.currentDir==='.')return;
   const parts=S.currentDir.split('/');