feat(workflow): add multi-CLI collaborative planning command

- Introduced a new command `/workflow:multi-cli-plan` for collaborative planning using ACE semantic search and iterative analysis with Claude and Codex.
- Implemented a structured execution flow with phases for context gathering, multi-tool analysis, user decision points, and final plan generation.
- Added detailed documentation outlining the command's usage, execution phases, and key features.
- Included error handling and configuration options for enhanced user experience.

ccw/src/templates/dashboard-css/21-cli-toolmgmt.css

@@ -661,3 +661,120 @@
   color: hsl(var(--success));
 }
 
+/* ========================================
+ * File Browser Modal
+ * ======================================== */
+
+.file-browser-modal {
+  width: 600px;
+  max-width: 90vw;
+  max-height: 80vh;
+  display: flex;
+  flex-direction: column;
+}
+
+.file-browser-toolbar {
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  padding: 0.5rem;
+  background: hsl(var(--muted) / 0.3);
+  border-radius: 0.375rem;
+  margin-bottom: 0.75rem;
+}
+
+.file-browser-toolbar .btn-sm {
+  flex-shrink: 0;
+  padding: 0.375rem;
+}
+
+.file-browser-path {
+  flex: 1;
+  padding: 0.375rem 0.5rem;
+  font-family: monospace;
+  font-size: 0.75rem;
+  background: hsl(var(--background));
+  border: 1px solid hsl(var(--border));
+  border-radius: 0.25rem;
+  color: hsl(var(--foreground));
+}
+
+.file-browser-hidden-toggle {
+  display: flex;
+  align-items: center;
+  gap: 0.375rem;
+  font-size: 0.75rem;
+  color: hsl(var(--muted-foreground));
+  cursor: pointer;
+  white-space: nowrap;
+}
+
+.file-browser-hidden-toggle input {
+  cursor: pointer;
+}
+
+.file-browser-list {
+  flex: 1;
+  min-height: 300px;
+  max-height: 400px;
+  overflow-y: auto;
+  border: 1px solid hsl(var(--border));
+  border-radius: 0.375rem;
+  background: hsl(var(--background));
+}
+
+.file-browser-loading,
+.file-browser-empty,
+.file-browser-error {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  height: 100%;
+  min-height: 200px;
+  color: hsl(var(--muted-foreground));
+  font-size: 0.875rem;
+}
+
+.file-browser-error {
+  color: hsl(var(--destructive));
+}
+
+.file-browser-item {
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  padding: 0.5rem 0.75rem;
+  cursor: pointer;
+  border-bottom: 1px solid hsl(var(--border) / 0.5);
+  transition: background-color 0.15s;
+}
+
+.file-browser-item:last-child {
+  border-bottom: none;
+}
+
+.file-browser-item:hover {
+  background: hsl(var(--muted) / 0.5);
+}
+
+.file-browser-item.selected {
+  background: hsl(var(--primary) / 0.15);
+  border-color: hsl(var(--primary) / 0.3);
+}
+
+.file-browser-item.is-directory {
+  color: hsl(var(--primary));
+}
+
+.file-browser-item.is-file {
+  color: hsl(var(--foreground));
+}
+
+.file-browser-item-name {
+  flex: 1;
+  font-size: 0.8125rem;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+