fix(app-boot): keep the fail-loud exit fatal while the terminal is released

Review of the previous commit found two defects in the release path, both
reproduced against the implementation:

- The timeout guarding a never-settling release was unref'ed. An
  unhandledRejection listener suppresses Node's default fatal exit, so with
  nothing else referenced the process reached an empty event loop and exited
  0 on the very failure it was reporting. Keep the timer referenced and clear
  it once the race settles.

- The handler uninstalled itself before awaiting the release. A second
  concurrent rejection then became uncaught and killed the process
  mid-teardown, stranding exactly the terminal state this restores. Replace
  the uninstall with a latch: the first rejection is the reported one, and
  later rejections (teardown's own included) fall through to the pending exit.

Add the PTY regression the fake-process tests cannot express: boot the shipped
tree over a fixture whose llm-pi-ai providers value is list-shaped, expect exit
1, and assert the captured bytes carry both the diagnostic and ESC[?2004l.
Against the pre-fix source the stream ends at ESC[?2004h ESC[>7u ESC[?u ESC[c
with no reset and the case fails, so it pins the actual bug.

Split the two-shape formatting test into one install per case; a latched
handler reports once by design.

apps/cli/tests/fixtures/tui-invalid-provider.cordis.yml

@@ -0,0 +1,10 @@
+# An overlay whose `llm-pi-ai` config fails schema validation: `providers` is a
+# dict keyed by provider name, and a list is the shape users reach for. The
+# entry rejects while `ui-tui` — mounted concurrently by the Loader — already
+# holds the terminal, which is the boot failure the fail-loud release hook
+# exists for.
+- id: llm-pi-ai
+  config:
+    providers:
+      - provider: openai
+        apiKey: keyless-invalid-shape

apps/cli/tests/tui-keyless-smoke.e2e.ts

@@ -24,6 +24,9 @@ const dshBinScript = fileURLToPath(new URL('../src/bin.ts', import.meta.url))
 // `--config` layers an overlay over the shared base, so the default surface
 // needs no config argument at all; these are the overlays under test.
 const scriptedConfigPath = fileURLToPath(new URL('./fixtures/tui-scripted.cordis.yml', import.meta.url))
+// An overlay whose `llm-pi-ai` config fails validation, so an entry rejects
+// while the TUI already holds the terminal.
+const invalidProviderConfigPath = fileURLToPath(new URL('./fixtures/tui-invalid-provider.cordis.yml', import.meta.url))
 const tsconfigPath = fileURLToPath(new URL('../../../tsconfig.json', import.meta.url))
 const firstRunSnapshots = fileURLToPath(new URL('./tui-first-run-snapshots/', import.meta.url))
 const synchronizedFrameEnd = '\x1b[?2026l'
@@ -380,6 +383,25 @@ describe('dsh TUI keyless smoke (real Loader tree in a PTY)', () => {
     expect(output).toContain('\u001B[?2004l')
   }, PTY_SMOKE_TEST_TIMEOUT_MS)
 
+  // The Loader mounts entries concurrently, so `ui-tui` can already own the
+  // terminal when a sibling entry rejects on its config. Exiting straight from
+  // the fail-loud handler left raw mode and bracketed paste set on the user's
+  // shell, and the pending Device Attributes reply landed there as literal
+  // text. The launcher's release hook must reach the TUI's own teardown.
+  it('restores the terminal when a sibling entry fails to validate during boot', async () => {
+    const output = await smoke({
+      label: 'dsh invalid provider config',
+      tempDirPrefix: 'dsh-tui-invalid-config-',
+      configPath: invalidProviderConfigPath,
+      expectedExitCode: 1,
+    })
+    expect(output).toContain('dsh: fatal load failure:')
+    expect(output).toContain('$.providers')
+    // Bracketed paste is disabled again, which only `ProcessTerminal.stop()`
+    // writes — proof the tree was disposed rather than exited out from under.
+    expect(output).toContain('\u001B[?2004l')
+  }, LOADER_SMOKE_TEST_TIMEOUT_MS)
+
   it('switches models, streams a response, answers a user-question dialog, and exits cleanly', async () => {
     const output = await smoke({
       label: 'dsh conversation',