release: finalize 0.15.0 validation and companion materials

Run conversation capture acceptance in a visible focused Electron window
and report concrete focus state on failure. Trigger Continue pre-spawn
cancellation at its existing environment callback instead of racing a timer.
Product implementation and approved bilingual note text remain unchanged.

Include the user's companion article updates and three reviewed draft images
as authorized. Keep their draft status and unverified build provenance clear.
Set the release date to September 28 and record the final real Linux result:
5345 passed, 51 skipped; Windows focused, typecheck, lint, and notes passed.

src/main/agent/continue-host-adapter.test.ts

@@ -319,6 +319,11 @@ describe('ContinueHostAdapter', () => {
   it('removes capability config when cancellation reaches the pre-spawn check', async () => {
     const distribution = await createDistribution()
     const launchHost = vi.fn<ContinueHostLauncher>()
+    const controller = new AbortController()
+    const launchEnvironmentProvider = vi.fn(() => {
+      controller.abort(new Error('cancelled'))
+      return {}
+    })
     const adapter = new ContinueHostAdapter({
       binaryPath: distribution.entryPath,
       configPath: '',
@@ -326,6 +331,7 @@ describe('ContinueHostAdapter', () => {
       cacheRoot: distribution.cacheRoot,
       trustedBundleHashes: [distribution.sourceHash],
       launchHost,
+      launchEnvironmentProvider,
       modelProfile: {
         id: '00000000-0000-4000-8000-000000000098',
         name: 'Local model',
@@ -335,7 +341,6 @@ describe('ContinueHostAdapter', () => {
         authentication: 'none'
       }
     })
-    const controller = new AbortController()
     const pending = adapter.run(
       'search',
       controller.signal,
@@ -348,9 +353,8 @@ describe('ContinueHostAdapter', () => {
         }
       }
     )
-    setTimeout(() => controller.abort(new Error('cancelled')), 0)
-
     await expect(pending).rejects.toThrow('cancelled')
+    expect(launchEnvironmentProvider).toHaveBeenCalledOnce()
     expect(launchHost).not.toHaveBeenCalled()
     await expect(readdir(distribution.cacheRoot)).resolves.not.toEqual(
       expect.arrayContaining([