feat: cherry-pick keyboard UX and file download from community PRs

Cherry-picked from PR #60 (keyboard UX) and PR #61 (file download):

- Alt+1-9 session switching
- Disable Ctrl+K (too easy to trigger accidentally)
- Session rename with prefix preservation (w1-case: description)
- Shift+Enter / Ctrl+Enter multiline input via tmux send-keys -H
- Android virtual keyboard fix for non-composition input
- File download button in browser file explorer (?download=true)

Dropped from PR #60: stale package-lock.json, upload popup (missing upload.html)
Dropped from PR #61: standalone /api/download endpoint (arbitrary fs access)
Fixed from PR #60: execFileSync replaced with async execFile

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

src/web/public/app.js

@@ -251,6 +251,23 @@ const _SSE_HANDLER_MAP = [
   [SSE_EVENTS.ORCHESTRATOR_ERROR, '_onOrchestratorError'],
 ];
 
+
+// ═══════════════════════════════════════════════════════════════
+// Session Name Prefix Parser
+// ═══════════════════════════════════════════════════════════════
+// Parses w<N>-<caseName> or s<N>-<caseName> prefix from session names.
+// Returns { prefix, suffix } or null if name does not match the pattern.
+function parseSessionPrefix(name) {
+  if (!name) return null;
+  const m = name.match(/^(w\d+-[a-zA-Z0-9_-]+|s\d+-[a-zA-Z0-9_-]+)/);
+  if (!m) return null;
+  const prefix = m[1];
+  const rest = name.slice(prefix.length);
+  if (rest === "") return { prefix, suffix: "" };
+  if (rest.startsWith(": ")) return { prefix, suffix: rest.slice(2) };
+  return null;
+}
+
 // ═══════════════════════════════════════════════════════════════
 // CodemanApp Class — constructor and global state
 // ═══════════════════════════════════════════════════════════════
@@ -615,10 +632,8 @@ class CodemanApp {
     //               shift? (require Shift), action }.
     const SHORTCUTS = [
       { key: '?', altKey: '/', ctrl: true, action: () => this.showHelp() },
-      { key: 'Enter', ctrl: true, action: () => this.quickStart() },
       { key: 'w', ctrl: true, action: () => this.killActiveSession() },
       { key: 'Tab', ctrl: true, action: () => this.nextSession() },
-      { key: 'k', ctrl: true, action: () => this.killAllSessions() },
       { key: 'l', ctrl: true, action: () => this.clearTerminal() },
       { key: 'R', ctrl: true, shift: true, action: () => this.restoreTerminalSize() },
       { key: '=', altKey: '+', ctrl: true, action: () => this.increaseFontSize() },
@@ -637,6 +652,16 @@ class CodemanApp {
         this.closeHelp();
       }
 
+      // Alt+1-9: switch to Codeman session by index
+      if (e.altKey && !e.ctrlKey && !e.shiftKey && e.key >= '1' && e.key <= '9') {
+        const idx = parseInt(e.key) - 1;
+        if (idx < this.sessionOrder.length) {
+          e.preventDefault();
+          this.selectSession(this.sessionOrder[idx]);
+        }
+        return;
+      }
+
       // Match against shortcut table
       for (const s of SHORTCUTS) {
         const keyMatch = e.key === s.key || (s.altKey && e.key === s.altKey);
@@ -1712,7 +1737,12 @@ class CodemanApp {
         // Update name if changed
         const nameEl = tab.querySelector('.tab-name');
         if (nameEl && nameEl.textContent !== name) {
-          nameEl.textContent = name;
+          const _p = parseSessionPrefix(name);
+          if (_p && _p.suffix) {
+            nameEl.innerHTML = '<span class="tab-prefix">' + escapeHtml(_p.prefix) + '</span><span class="tab-suffix">: ' + escapeHtml(_p.suffix) + '</span>';
+          } else {
+            nameEl.textContent = name;
+          }
         }
 
         // Update task badge
@@ -1820,7 +1850,7 @@ class CodemanApp {
           <span class="tab-info">
             <span class="tab-name-row">
               ${mode === 'shell' ? '<span class="tab-mode shell" aria-hidden="true">sh</span>' : mode === 'opencode' ? '<span class="tab-mode opencode" aria-hidden="true">oc</span>' : ''}
-              <span class="tab-name" data-session-id="${id}">${escapeHtml(name)}</span>
+              <span class="tab-name" data-session-id="${id}">${(() => { const p = parseSessionPrefix(name); return p && p.suffix ? '<span class="tab-prefix">' + escapeHtml(p.prefix) + '</span><span class="tab-suffix">: ' + escapeHtml(p.suffix) + '</span>' : escapeHtml(name); })()}</span>
             </span>
             ${showFolder ? `<span class="tab-folder">\u{1F4C1} ${escapeHtml(folderName)}</span>` : ''}
           </span>