fix: harden core build system against silent failures

- Wrap rebuild() in try/finally to guarantee mutex release (prevents deadlock)
- Surface rebuild errors via .catch() instead of discarding with void
- Add null checks for vfile.data.relativePath (prevents crash on virtual files)
- Add try-finally for worker pool cleanup in parse.ts (prevents thread leaks)
- Remove process.exit(1) from parse error handler (let errors propagate)
- Add per-emitter error handling in emit phase with degraded-build warning
- Replace unsafe Map.get()! assertions with null-checked access in config-loader

quartz/plugins/loader/config-loader.ts

@@ -854,10 +854,13 @@ function resolveGroups(
         const groupConfig = groups[item.group]
         groupPriority.set(item.group, groupConfig?.priority ?? item.priority)
       }
-      groupedComponents.get(item.group)!.push({
-        component: item.component,
-        groupOptions: item.groupOptions,
-      })
+      const groupMembers = groupedComponents.get(item.group)
+      if (groupMembers) {
+        groupMembers.push({
+          component: item.component,
+          groupOptions: item.groupOptions,
+        })
+      }
     }
   }
 
@@ -873,7 +876,8 @@ function resolveGroups(
       if (processedGroups.has(item.group)) continue
       processedGroups.add(item.group)
 
-      const members = groupedComponents.get(item.group)!
+      const members = groupedComponents.get(item.group)
+      if (!members) continue
       const groupConfig = groups[item.group] ?? {}
 
       const flexComponents = members.map((m) => ({
@@ -896,7 +900,7 @@ function resolveGroups(
         gap: groupConfig.gap ?? "1rem",
       }) as QuartzComponent
 
-      entries.push({ priority: groupPriority.get(item.group)!, component: flexComponent })
+      entries.push({ priority: groupPriority.get(item.group) ?? 50, component: flexComponent })
     } else {
       entries.push({ priority: item.priority, component: item.component })
     }