feat: engine/model in audit log + docs update

- tool_audit: ContextVars (engine, model) set at orchestrator run start; fields added to every entry
- orchestrator_engine: tool_audit.set_context("gemini", model_name) at run() start
- openai_orchestrator: tool_audit.set_context("openai", model label) at run() start
- audit table: Model column between Status and Args
- HELP.md: push notifications section, audit log in Files section, tool count 30→40, new API endpoints
- TODO__Agents.md: web_push and audit log marked complete with full detail

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

cortex/static/app.js

@@ -1547,6 +1547,7 @@
                 <th class="at-time">Time</th>
                 <th class="at-tool">Tool</th>
                 <th class="at-status">Status</th>
+                <th class="at-model">Model</th>
                 <th class="at-args">Args</th>
                 <th class="at-result">Result</th>
             </tr></thead>`;
@@ -1554,11 +1555,13 @@
             const tbody = document.createElement('tbody');
             for (const e of entries) {
                 const time = (e.ts || '').slice(11, 19); // HH:MM:SS
+                const model = e.model || e.engine || '';
                 const tr = document.createElement('tr');
                 tr.innerHTML = `
                     <td class="at-time">${time}</td>
                     <td class="at-tool" title="${e.tool || ''}">${e.tool || '?'}</td>
                     <td class="${_auditStatusClass(e.status)}">${e.status || '?'}</td>
+                    <td class="at-model" title="${model}">${model}</td>
                     <td class="at-args" title="${(_fmtArgs(e.args) || '').replace(/"/g, '&quot;')}">${_fmtArgs(e.args)}</td>
                     <td class="at-result" title="${(e.result_snippet || '').replace(/</g, '&lt;').replace(/"/g, '&quot;')}">${
                         (e.result_snippet || '').replace(/</g, '&lt;').slice(0, 80)