put the monitor scope in the url

/system-monitor/:scope, the same shape as /photos: route pair, one Navigate guard after the
hooks, scope list as react-router NavLinks, and both panels reading useParams instead of
agreeing over a `monitor:scope` channel. The Dock's isActive is a startsWith, so its
highlight survives the redirect off the bare route.

docs/workspace-panel-todo.md

@@ -644,8 +644,10 @@ All the same bug: an app guessing "am I being closed?" from an unmount, or payin
       could never have worked: the link set the section, the tab stayed on Enterprise, and the content
       pane rendered "Select a section" for a section that existed. The tab is derived from the section
       key now, so there is nothing left to disagree with.
-      Remaining here: Music, Soulseek, SystemMonitor, Email, Browser. **Chat detail
-      (`chat:selected-session`) is chat-owned — leave it; it is written up in `COMMS/`.**
+      **SystemMonitor is done too** (audit M10) — `/system-monitor/:scope`, scope list as `NavLink`s,
+      `monitor:scope` deleted. Smallest of the seven and the same shape as `/photos`.
+      Remaining here: Music, Soulseek, Email, Browser. **Chat detail (`chat:selected-session`) is
+      chat-owned — leave it; it is written up in `COMMS/`.**
 
 ### 5.9 The context has grown an app-config section — _(found 2026-08-07)_