Add structured headers to the PHP pages layer

Documents each tab's purpose, what it renders, and which endpoints it polls.
Pages that start with markup get the header in a <?php ?> block so it never
reaches the browser.

Also corrects the layer diagram in README-unraid.md: eight of eleven pages hold
no PHP logic and poll api/ for everything — only auth, monitor and scheduler
require an include/ file directly.

Plugin/unraid/pages/partnership.php

@@ -1,3 +1,41 @@
+<?php
+// ═══════════════════════════════════════════════════════════════════════════════════════════════
+// PURPOSE
+//   Partnership tab. The mesh view — which nodes exist, whether they are reachable over
+//   Tailscale, their system summary, sync history, and the onboarding controls that deploy
+//   stacks to a partner.
+//
+// DESIGN PRINCIPLES
+//   Pure view — all node data comes from api/partnership.php; actions are separate endpoints.
+//   Reachability, SSH and system collection live in include/partnership.php.
+//
+//   Reachability is probed on demand as well as polled, because "is my partner up right now"
+//   is the question this page exists to answer.
+//
+// OPERATIONAL SAFEGUARDS
+//   Every action that changes a partner is confirmed first — this page can deploy stacks and
+//   provision credentials on a machine 50 miles away, and there is no undo for that.
+//
+//   Long-running operations go through api/run.php rather than blocking the page, so a deploy
+//   that takes minutes does not leave the browser hanging on a request.
+//
+//   An unreachable partner degrades to its own card only; the rest of the mesh still renders.
+//
+//   Values from remote nodes are escaped on render — this page displays strings originating
+//   on another machine.
+//
+// RENDERS
+//   Node cards with identity, reachability, system summary, sync history
+//   Onboarding and stack-deploy controls, API key provisioning, partnership settings
+//
+// DEPENDS ON
+//   api/partnership.php           polled every 10s   → include/partnership.php
+//   api/partnership_ping.php      on-demand reachability probe
+//   api/partnership_settings.php  settings writes
+//   api/create_api_key.php        credential provisioning
+//   api/run.php                   long-running deploy operations
+//   api/confform.php              inline conf edits
+?>
 <style>
 .vv-pt-grid       { display:grid; gap:12px; }
 .vv-pt-node       { background:#161616; border:1px solid #2a2a2a; border-radius:6px; padding:12px; min-width:0; }