Collector auto-links measuring tools for metrology PCs; settings rail cleanup

Metrology PCs (CMM, Keyence, Genspect, wax-and-trace imaging pc-types) drive
an attached measuring instrument. The PC itself stays a shopfloor PC, but the
collector now models the instrument:

- New METROLOGY_TOOL_MAP (pctypemap.py) maps those pc-types to a
  MeasuringToolType (CMM, Vision System, Genspect, Form Tracer).
- ComputersPlugin._sync_measuringtool_link creates the MeasuringTool asset
  once and a directional PC->tool "controls" relationship, tagged
  collector:measuringtool. Idempotent (re-push reuses, no duplicate asset) and
  self-archiving (a PC re-imaged to a non-metrology type deactivates the link
  but keeps the asset and any calibration history). Mirrors the printer-link
  pattern. The MeasuringToolType is created on demand if not seeded.
- 4 tests: create+link, idempotent re-push, non-metrology skip, repurpose
  archives. Non-metrology PCs never warn about a missing controls type.

Settings rail cleanup:
- Collapsible groups so the 13-group rail fits without scrolling (1511px ->
  488px). The group containing the current page expands; the rest collapse.
  CSS-drawn caret (ASCII source, no Unicode). Empty groups never render, in
  both the rail and the landing page.
- Measuring Tools group placed with the other asset groups (right after
  Machines) instead of appended last; empty placeholder positions the
  plugin-contributed cards.
- Operating Systems moved from PCs to General Reference: OS is cross-asset
  (PCs, machines, measuring tools, network devices all run one).

Plus docs/proposals/ge-enforce-plugin.md: a planning doc for refactoring
GE-Enforce/DSC into a shopdb plugin (manifest as shopdb data, payloads on
SMB/HTTP/inline), grounded in the real manifest schema.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/views/settings/settingsNav.js

@@ -26,13 +26,15 @@ export const settingsGroups = [
       { to: '/settings/assettypes', icon: Palette, title: 'Asset Type Colors', description: 'Map colors for the top-level asset categories' },
       { to: '/settings/customfields', icon: SlidersHorizontal, title: 'Custom Fields', description: 'Define extra attributes per asset type (shown on detail + forms)' },
       { to: '/settings/supportteams', icon: Users, title: 'Support Teams', description: 'Application support teams and their contacts (ServiceNow group links)' },
+      // Operating Systems is cross-asset (PCs, machines, measuring tools, network
+      // devices all run an OS), so it lives in General Reference, not under PCs.
+      { to: '/settings/operatingsystems', icon: Cog, title: 'Operating Systems', description: 'Manage OS versions and EOL dates (used by PCs, machines, network devices, and more)' },
     ],
   },
   {
     title: 'PCs',
     cards: [
       { to: '/settings/pctypes', icon: Laptop, title: 'PC Types', description: 'Manage PC form factors + map colors' },
-      { to: '/settings/operatingsystems', icon: Cog, title: 'Operating Systems', description: 'Manage OS versions and EOL dates' },
       { to: '/settings/accessprotocols', icon: Network, title: 'PC Access Protocols', description: 'Remote-access protocols (VNC, RDP, WinRM) and link templates' },
     ],
   },
@@ -50,9 +52,16 @@ export const settingsGroups = [
       { to: '/settings/machinetypes', icon: Wrench, title: 'Machine Types', description: 'Manage machine subtypes + map colors' },
     ],
   },
-  // The "Measuring Tools" group is contributed by the measuringtools plugin via
-  // the ADR-010 get_settings_cards hook (merged in composables/settingsCatalog),
-  // not hardcoded here.
+  // The "Measuring Tools" cards are contributed by the measuringtools plugin via
+  // the ADR-010 get_settings_cards hook (merged in composables/settingsCatalog).
+  // This empty placeholder fixes the group's position among the asset groups
+  // (right after Machines); the merger fills it in place instead of appending a
+  // new group at the end. When the plugin is disabled the group stays empty and
+  // the rail/landing drop it (empty groups never render).
+  {
+    title: 'Measuring Tools',
+    cards: [],
+  },
   {
     title: 'Locations & Organization',
     cards: [