fix(settings): keep installSettingsSection quiet when its consumer unloads

The helper's cleanup ran the same fallback for two different events. A
settings provider detaching leaves the consumer running, so falling back
to the composition entry and re-judging derived facts is right. The
consumer's own unload ran it too — re-registering routes and touching
resources the teardown was releasing. The disposer now checks the
consumer fiber's own state and returns when it is unloading or disposed.

packages/settings/settings/src/index.ts

@@ -538,6 +538,20 @@ export abstract class Settings extends Service {
   }
 }
 
+/**
+ * Value mirror of the `FiberState` members {@link isUnloading} compares
+ * against: a const enum has no runtime object to import, and the value is
+ * needed at runtime (same rationale as the CLI boot driver's mirror).
+ */
+const FIBER_DISPOSED = 4
+const FIBER_UNLOADING = 5
+
+/** Whether the consumer's own fiber is tearing down (not just losing the settings service). */
+function isUnloading(ctx: Context): boolean {
+  const state: number = ctx.fiber.state
+  return state === FIBER_UNLOADING || state === FIBER_DISPOSED
+}
+
 /** Hooks a consumer hands to {@link installSettingsSection}. */
 export interface SettingsSectionHooks<T> {
   /**
@@ -578,6 +592,13 @@ export function installSettingsSection<T>(
     const scope = sctx.settings.register(ns, schema, { base: entry })
     hooks.setSource(() => scope.get())
     sctx.effect(() => () => {
+      // This disposer runs for two different reasons. A settings provider
+      // detaching leaves the consumer running, so it must fall back to its
+      // composition entry and re-judge what it derived. The consumer's own
+      // unload runs it too — and there `onChange` would re-register routes
+      // and touch resources the teardown is releasing, so the fallback is
+      // pointless and the notification actively harmful.
+      if (isUnloading(ctx)) return
       hooks.setSource(() => entry)
       hooks.onChange()
     })

packages/settings/settings/tests/settings.spec.ts

@@ -694,4 +694,34 @@ describe('installSettingsSection', () => {
     })
     expect(current()).toEqual({ theme: 'entry' })
   })
+
+  it('stays silent when the consumer itself unloads', async () => {
+    const { ctx } = await boot({ doc: { 'helper-ns': { theme: 'user' } } })
+    const entry = { theme: 'entry' }
+    let current: () => { theme: string } = () => entry
+    const changes: string[] = []
+    const consumer = ctx.plugin({
+      inject: ['settings'],
+      apply: (child: Context) => {
+        installSettingsSection(child, settingsNamespace('helper-ns'), HelperSchema, entry, {
+          setSource: (source) => {
+            current = source
+          },
+          onChange: () => {
+            changes.push(current().theme)
+          },
+        })
+      },
+    })
+    await consumer
+    await vi.waitFor(() => {
+      expect(changes).toEqual(['user'])
+    })
+
+    // The consumer's own teardown must not re-derive anything: an onChange
+    // here would re-register routes and touch resources being released.
+    await consumer.dispose()
+    await new Promise(resolve => setTimeout(resolve, 20))
+    expect(changes).toEqual(['user'])
+  })
 })