release: validate the complete 0.15.0 branch snapshot

Account for concurrent composer, conversation-order, desktop-notification,
and Supervisor discussion changes in bilingual notes and feature matrices.
Correct the removed entity-writeback description in the companion article.

Align the configuration fixture with the default-on notification setting,
scope note-source UI queries and wait for completed actions, and preserve
all real Obsidian child-process checks with a 15-second scenario allowance.

Validation: frozen complete tree passed 5371 Linux tests with 51 skipped;
19 focused Windows tests, typecheck, lint, and release-note validation passed.
The older 5345-test Host result did not cover all concurrent branch changes
and is not treated as validation of this complete candidate.

src/shared/goodbuddy-config-contracts.test.ts

@@ -152,6 +152,7 @@ describe('GoodBuddy configuration contracts', () => {
     const snapshot = {
       application: {
         checkUpdatesOnStartup: true,
+        desktopNotificationsEnabled: true,
         updateSource: 'github',
         modelDownloadSource: 'modelscope',
         localToolEnvironment: defaultLocalToolEnvironmentSettings,