agent terminal: slash commands /help and /clear, tab-completion

intercept any line starting with / before sending it to the agent inbox.
two commands today:
- /help — render command list locally
- /clear — wipe the local terminal view (server-side event history kept,
  so a page reload restores it)

unknown /xxx surfaces an error row instead of being silently sent. tab
on a /prefix cycles through matching command names. submit-hint
mentions /help so the operator can discover it.

scaffolding for the bigger commands (/compact /cancel /model) is in
place — adding them later is a switch arm plus harness work.

hive-ag3nt/assets/app.js

@@ -155,6 +155,47 @@
   let lastOutputLen = -1;
   let pollTimer = null;
   let termInputRendered = false;
+  // Filled in by the live-event IIFE below. Used by the slash-command
+  // dispatcher to print local-only rows ('help', errors) and to clear
+  // the terminal on `/clear`.
+  let termAPI = null;
+
+  const SLASH_COMMANDS = [
+    { name: '/help',  desc: 'list slash commands' },
+    { name: '/clear', desc: 'wipe the terminal panel (local-only)' },
+  ];
+
+  function handleSlashCommand(line) {
+    if (!termAPI) return false;
+    const trimmed = line.trim();
+    if (!trimmed.startsWith('/')) return false;
+    const [cmd] = trimmed.split(/\s+/);
+    switch (cmd) {
+      case '/help':
+        termAPI.row('note', '· /help');
+        for (const c of SLASH_COMMANDS) {
+          termAPI.row('note', '    ' + c.name.padEnd(10) + ' — ' + c.desc);
+        }
+        return true;
+      case '/clear':
+        termAPI.clear();
+        termAPI.row('note', '· terminal cleared (local view only — server history kept)');
+        return true;
+      default:
+        termAPI.row('turn-end-fail', '✗ unknown slash command: ' + cmd + ' — try /help');
+        return true;
+    }
+  }
+
+  // Cycle through commands when operator hits Tab on a `/…` prefix.
+  function completeSlash(prefix) {
+    const matches = SLASH_COMMANDS.filter((c) => c.name.startsWith(prefix));
+    if (!matches.length) return null;
+    // Cycle: when the current prefix already equals a command name,
+    // advance to the next match.
+    const idx = matches.findIndex((c) => c.name === prefix);
+    return matches[(idx + 1) % matches.length].name;
+  }
 
   function renderTermInput(label, online) {
     const slot = $('term-input');
@@ -178,9 +219,24 @@
       };
       ta.addEventListener('input', grow);
       ta.addEventListener('keydown', (e) => {
+        // Tab-complete slash commands when the buffer starts with `/`.
+        if (e.key === 'Tab' && ta.value.startsWith('/') && !ta.value.includes(' ')) {
+          const next = completeSlash(ta.value);
+          if (next) { e.preventDefault(); ta.value = next; return; }
+        }
         if (e.key === 'Enter' && !e.shiftKey && !e.isComposing) {
           e.preventDefault();
-          if (ta.value.trim()) form.requestSubmit();
+          const line = ta.value;
+          if (!line.trim()) return;
+          // Intercept slash commands locally; never send them to the agent.
+          if (line.trim().startsWith('/')) {
+            if (handleSlashCommand(line)) {
+              ta.value = '';
+              grow();
+              return;
+            }
+          }
+          form.requestSubmit();
         }
       });
       // Reset height after async submit clears the value.
@@ -188,7 +244,7 @@
       form.append(
         el('span', { class: 'prompt' }, 'operator@' + label + ' ▸'),
         ta,
-        el('span', { class: 'submit-hint' }, '↵ send · ⇧↵ newline'),
+        el('span', { class: 'submit-hint' }, '↵ send · ⇧↵ newline · /help'),
       );
       slot.append(form);
       termInputRendered = true;
@@ -270,6 +326,11 @@
     // Backfill replays mark rows .no-anim so we don't stagger 100 fade-ins
     // on page load. Set via `currentNoAnim` before the row helpers fire.
     let currentNoAnim = false;
+    // Expose the panel API for slash commands (`/help`, `/clear`).
+    termAPI = {
+      row: (cls, text) => row(cls, text),
+      clear: () => { log.innerHTML = ''; placeholder = null; },
+    };
     function row(cls, text) {
       clearPlaceholder();
       const e = document.createElement('div');