test(host): drain Include write queue in picker composition spec

Replace the debounce-timer polling with Include.stop(), which flushes the
file-backed write queue deterministically. This avoids Windows coverage
flakes where the self-dispose write could land after the expect.poll
timeout.

packages/host/directory-picker-auto/tests/loader-composition.spec.ts

@@ -138,6 +138,14 @@ function entryNames(ctx: Context): string[] {
   return [...ctx.loader.entries()].map(entry => entry.options.name)
 }
 
+/** The Include tree that backs the booted `cordis.yml` file. */
+function includeTree(ctx: Context): Include {
+  const include = [...ctx.loader.entries()]
+    .find(entry => entry.options.name === 'cordis:include')?.subtree as Include | undefined
+  if (include === undefined) throw new Error('expected the root Include tree')
+  return include
+}
+
 /**
  * Force every signal of an attended host on any platform: no SSH launch, a
  * display, and a PATH holding one executable chooser binary so the real
@@ -188,10 +196,10 @@ describe('real Loader composition', () => {
     // behavior, not the chooser's); await that debounced write so it cannot
     // race the temp-dir removal, and pin that the persisted row is the
     // chooser itself — the resolved backend still never reaches the file.
-    await expect.poll(
-      async () => await readFile(configPath, 'utf8'),
-      { timeout: 15_000 },
-    ).toContain('disabled: true')
+    // stop() drains the Include write queue, so this assertion does not depend
+    // on the debounce timer racing Windows coverage load.
+    await includeTree(ctx).stop()
+    expect(await readFile(configPath, 'utf8')).toContain('disabled: true')
     expect(await readFile(configPath, 'utf8')).not.toContain(NATIVE)
   })
 
@@ -240,8 +248,10 @@ describe('real Loader composition', () => {
     await expect(autoEntry.fiber!.dispose()).resolves.not.toThrow()
     expect(entryNames(ctx)).not.toContain(NATIVE)
     expect(entryNames(ctx)).not.toContain(NATIVE_SURFACE)
-    // Same self-dispose persistence as above: let the write land before teardown.
-    await expect.poll(async () => await readFile(configPath, 'utf8')).toContain('disabled: true')
+    // Same self-dispose persistence as above: drain the Include write queue
+    // deterministically before asserting the persisted row.
+    await includeTree(ctx).stop()
+    expect(await readFile(configPath, 'utf8')).toContain('disabled: true')
     expect(renameControl.injectedFailures).toBe(1)
     expect(renameControl.remainingFailures).toBe(0)
     expect(renameControl.attempts).toBeGreaterThanOrEqual(2)
@@ -251,9 +261,7 @@ describe('real Loader composition', () => {
     stubAttendedHost()
     const { ctx } = await loadComposition('127.0.0.1')
     const autoEntry = [...ctx.loader.entries()].find(entry => entry.options.name === AUTO)!
-    const include = [...ctx.loader.entries()]
-      .find(entry => entry.options.name === 'cordis:include')?.subtree as Include | undefined
-    if (include === undefined) throw new Error('expected the root Include tree')
+    const include = includeTree(ctx)
     renameControl.failureCode = 'EIO'
     renameControl.remainingFailures = 1