feat(chat): slash-command autocomplete

Typing / opens a command panel from the guild's synced OpenClaw catalog
(GET /api/commands): filter + ↑↓/Enter/Esc; pick inserts /<nativeName> ;
arg stage lists args (required/type/desc) with clickable choice chips
(dynamic choices already snapshotted server-side). Sent as a normal
message — execution flows plugin -> OpenClaw command system.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/index.css

@@ -995,3 +995,88 @@ textarea.canvas-src {
   max-width: 720px;
   width: 92vw;
 }
+
+/* ---- slash command autocomplete ---- */
+.slash-panel {
+  border: 1px solid var(--border);
+  border-bottom: 0;
+  background: var(--elevated);
+  border-radius: var(--radius-sm) var(--radius-sm) 0 0;
+  max-height: 320px;
+  overflow: auto;
+  padding: 6px;
+}
+.slash-panel .slash-hint {
+  font-size: 11px;
+  color: var(--text-faint);
+  padding: 4px 8px 6px;
+  text-transform: uppercase;
+  letter-spacing: 0.04em;
+}
+.slash-item {
+  display: flex;
+  gap: 10px;
+  align-items: baseline;
+  width: 100%;
+  text-align: left;
+  background: none;
+  border: 0;
+  color: var(--text);
+  padding: 7px 8px;
+  border-radius: 5px;
+  cursor: pointer;
+}
+.slash-item.sel,
+.slash-item:hover {
+  background: var(--accent-soft);
+}
+.slash-item .sc-name {
+  font-family: var(--mono);
+  font-size: 13px;
+  color: var(--text-h);
+  white-space: nowrap;
+}
+.sc-desc {
+  font-size: 12px;
+  color: var(--text-muted);
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+.slash-arg {
+  padding: 6px 8px;
+  border-top: 1px solid var(--border);
+}
+.slash-arg .sa-name {
+  font-family: var(--mono);
+  font-size: 13px;
+  color: var(--text-h);
+}
+.slash-arg .sa-req {
+  color: var(--danger);
+  margin-left: 1px;
+}
+.slash-arg .sa-type {
+  font-size: 11px;
+  color: var(--text-faint);
+  margin: 0 8px;
+}
+.sa-choices {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 6px;
+  margin-top: 6px;
+}
+.sa-choice {
+  font-size: 12px;
+  background: var(--input);
+  border: 1px solid var(--border);
+  color: var(--text);
+  padding: 3px 8px;
+  border-radius: 999px;
+  cursor: pointer;
+}
+.sa-choice:hover {
+  border-color: var(--accent);
+  color: var(--text-h);
+}