feat: per-role inject_mode, OTR fixes, hover metadata, send/stop tooltip

- inject_mode: per-role toggle (parallel to inject_datetime) gates the
  "Current mode: Off The Record" line in the system prompt; wired through
  model_registry, context_loader, chat router, orchestrator router, and
  local_llm settings UI

- OTR orchestrator fix: OrchestrateRequest now carries off_record;
  _finalize_job stores it per message and gates log_turn on it; JS
  orchestrate payload sends off_record correctly

- Per-message hover metadata: removed always-visible .model-tag; replaced
  with .msg-meta strip in the action bar (hover-only); shows model label,
  host, fallback indicator, and OTR badge; stored in session JSON

- Send/stop button tooltip: shows role + model and (when tools on)
  separate orchestrator model + engine label; live elapsed timer on stop
  button via startRunTimer/stopRunTimer

- OrchestratorResult.backend_label: new field; openai_orchestrator fills
  it; finalize_job propagates it to job dict and session messages

- GET /backend: exposes orchestrator_model label so the frontend tooltip
  can show both models separately

- TODO: session delete confirmation added

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cortex/static/local_llm.html

@@ -634,6 +634,9 @@
       // Inject datetime checkbox (default true if not set)
       const dtCb = panel.querySelector('.rcp-datetime-cb');
       if (dtCb) dtCb.checked = cfg.inject_datetime !== false;
+      // Inject mode checkbox (default true if not set)
+      const modeCb = panel.querySelector('.rcp-mode-cb');
+      if (modeCb) modeCb.checked = cfg.inject_mode !== false;
       // Build tool checklist
       buildToolChecklist(role, cfg.tools || null);
       panel.classList.add('open');
@@ -674,6 +677,8 @@
         const ta     = panel.querySelector('.rcp-textarea');
         const dtCb   = panel.querySelector('.rcp-datetime-cb');
         const inject_datetime = dtCb ? dtCb.checked : true;
+        const modeCb = panel.querySelector('.rcp-mode-cb');
+        const inject_mode = modeCb ? modeCb.checked : true;
         const checks = [...panel.querySelectorAll('.rcp-tools input[type=checkbox]')];
         const allChecked  = checks.every(c => c.checked);
         const someChecked = checks.some(c  => c.checked);
@@ -684,7 +689,7 @@
           const res  = await fetch('/api/models/role-config', {
             method: 'POST',
             headers: {'Content-Type': 'application/json'},
-            body: JSON.stringify({role, system_append: ta.value, tools, inject_datetime}),
+            body: JSON.stringify({role, system_append: ta.value, tools, inject_datetime, inject_mode}),
           });
           const data = await res.json();
           if (data.ok) {
@@ -693,6 +698,7 @@
             ROLE_CONFIG_DATA[role].system_append = ta.value;
             ROLE_CONFIG_DATA[role].tools = tools;
             ROLE_CONFIG_DATA[role].inject_datetime = inject_datetime;
+            ROLE_CONFIG_DATA[role].inject_mode = inject_mode;
             showToast(`${role} config saved`);
             closeRolePanel(role);
           } else {