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/SettingsLayout.vue

@@ -10,17 +10,27 @@
 
       <nav class="rail-nav">
         <template v-for="group in visibleGroups" :key="group.title">
-          <div class="rail-group-heading">{{ group.title }}</div>
-          <router-link
-            v-for="card in group.cards"
-            :key="card.to"
-            :to="card.to"
-            class="rail-link"
-            :class="{ active: isActive(card.to) }"
+          <button
+            type="button"
+            class="rail-group-heading"
+            :class="{ collapsed: !isExpanded(group.title) }"
+            @click="toggleGroup(group.title)"
           >
-            <span class="rail-icon"><component :is="card.icon" :size="16" /></span>
-            <span class="rail-label">{{ card.title }}</span>
-          </router-link>
+            <span class="rail-chevron" aria-hidden="true"></span>
+            {{ group.title }}
+          </button>
+          <template v-if="isExpanded(group.title)">
+            <router-link
+              v-for="card in group.cards"
+              :key="card.to"
+              :to="card.to"
+              class="rail-link"
+              :class="{ active: isActive(card.to) }"
+            >
+              <span class="rail-icon"><component :is="card.icon" :size="16" /></span>
+              <span class="rail-label">{{ card.title }}</span>
+            </router-link>
+          </template>
         </template>
         <p v-if="!visibleGroups.length" class="rail-empty">No matching settings</p>
       </nav>
@@ -48,7 +58,9 @@ const search = ref('')
 // Filter the rail by title/description; drop groups that end up empty.
 const visibleGroups = computed(() => {
   const term = search.value.trim().toLowerCase()
-  if (!term) return groups.value
+  // Drop empty groups (e.g. the Measuring Tools placeholder when its plugin is
+  // disabled) so a bare heading never renders.
+  if (!term) return groups.value.filter(g => g.cards.length)
   return groups.value
     .map(g => ({
       title: g.title,
@@ -65,6 +77,25 @@ function isActive(to) {
   const base = to.split('?')[0]
   return route.path === base
 }
+
+// Collapsible groups so the 13-section rail fits without scrolling: only the
+// group containing the current page is open; the user can toggle others.
+// Searching forces every matching group open.
+const groupOfActive = computed(() => {
+  for (const g of groups.value) {
+    if (g.cards.some(c => isActive(c.to))) return g.title
+  }
+  return groups.value[0]?.title
+})
+const manualToggles = ref({})
+function toggleGroup(title) {
+  manualToggles.value = { ...manualToggles.value, [title]: !isExpanded(title) }
+}
+function isExpanded(title) {
+  if (search.value.trim()) return true
+  if (title in manualToggles.value) return manualToggles.value[title]
+  return title === groupOfActive.value
+}
 </script>
 
 <style scoped>
@@ -82,11 +113,11 @@ function isActive(to) {
   overflow-y: auto;
 }
 .rail-title {
-  margin: 0 0 0.75rem 0;
-  font-size: 1.5rem;
+  margin: 0 0 0.5rem 0;
+  font-size: 1.25rem;
 }
 .rail-search {
-  margin-bottom: 0.75rem;
+  margin-bottom: 0.5rem;
 }
 .search-input {
   width: 100%;
@@ -99,26 +130,52 @@ function isActive(to) {
 }
 
 .rail-group-heading {
-  margin: 1rem 0 0.3rem 0;
+  display: flex;
+  align-items: center;
+  gap: 0.35rem;
+  width: 100%;
+  margin: 0.35rem 0 0.15rem 0;
+  padding: 0.2rem 0;
   font-size: 0.68rem;
   font-weight: 700;
   letter-spacing: 0.06em;
   text-transform: uppercase;
   color: var(--text-light);
+  background: none;
+  border: none;
+  cursor: pointer;
+  text-align: left;
+}
+.rail-group-heading:hover {
+  color: var(--text);
 }
 .rail-group-heading:first-child {
   margin-top: 0;
 }
+/* CSS-drawn caret (ASCII-only source): a right-pointing triangle that
+   rotates down when the group is expanded. */
+.rail-chevron {
+  width: 0;
+  height: 0;
+  flex: 0 0 auto;
+  border-top: 4px solid transparent;
+  border-bottom: 4px solid transparent;
+  border-left: 5px solid currentColor;
+  transition: transform 0.12s ease;
+}
+.rail-group-heading:not(.collapsed) .rail-chevron {
+  transform: rotate(90deg);
+}
 
 .rail-link {
   display: flex;
   align-items: center;
   gap: 0.5rem;
-  padding: 0.4rem 0.55rem;
+  padding: 0.25rem 0.55rem;
   border-radius: 6px;
   text-decoration: none;
   color: var(--text);
-  font-size: 0.88rem;
+  font-size: 0.86rem;
   border-left: 2px solid transparent;
 }
 .rail-link:hover {