feat(panel): adaptive monitoring poll intervals (v1.x closure phase 1)

Replace fixed 5 s hx-trigger polling with data-poll markers and panel.js
scheduling: 5 s while active, 30 s when idle, none when tab is hidden.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

internal/web/templates/status.html

@@ -44,7 +44,7 @@
 
 {{/* The status page's section index, shown in the navigation column (see the
      "sections" block in layout.html). The first six cards are the ones the
-     polling fragment replaces every five seconds; their ids are part of
+     polling fragment replaces on a timer; their ids are part of
      status_body.html and do not change with the reading, so the links here hold
      across a refresh. */}}
 {{define "sections"}}