test(daemon): add F1/F2 process-lifecycle integration tests; fix clobbered start error

Links the real EmbeddedDaemon into the ObsidianDragonTests target (its deps were
already present) and adds two POSIX integration tests that exercise the actual
fork/exec/waitpid fixes headlessly:

- testExecFailureReported (F2): start() against a non-executable file must fail with a
  precise "not executable or wrong architecture" reason.
- testDaemonCrashDetected (F1): a short-lived child that exits abnormally is still
  detected (crash_count_ increments) while isRunning() is hammered from the test
  thread — a regression test for the reap race.

Writing the F2 test surfaced a real bug: start()'s failure branch called
setState(State::Error, "Failed to start dragonxd process"), and setState stores the
Error message into last_error_ — clobbering the precise message startProcess() had
just set, so getLastError()/the UI only ever saw the generic string. Fixed to pass the
preserved detail to setState, so the precise reason survives and now also reaches the
state callback (crash panel / status).

ctest 1/1, green including the two new integration tests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/daemon-startup-hardening.md

@@ -24,9 +24,9 @@ back-fill applied additively to `res/lang/*.json` (42 keys — all 6 for es/de/f
 entries whose glyphs aren't in the current `NotoSansCJK-Subset.ttf` were left on English fallback
 rather than render as tofu).
 
-**Still owed before release:** the F1/F2 manual repros (`kill -SEGV` / non-executable binary — not
-unit-testable), and a **CJK subset-font rebuild** (`scripts/build_cjk_subset.py`, needs the Noto
-CJK source font) to cover those 6 deferred zh/ja/ko strings.
+**Still owed before release:** a **CJK subset-font rebuild** (`scripts/build_cjk_subset.py`, needs
+the Noto CJK source font) to cover the 6 deferred zh/ja/ko strings. *(F1 and F2 now have headless
+integration-test coverage — see the progress log — so their GUI repros are optional, not blocking.)*
 
 ---
 
@@ -537,6 +537,8 @@ design record; see the shared-helper table above.
 
 ## Progress log
 
+- **F1/F2 integration tests** — ☑ added `testExecFailureReported` (F2) and `testDaemonCrashDetected` (F1) to `test_phase4.cpp`, driving the **real** `EmbeddedDaemon` fork/exec/waitpid code headlessly (POSIX; required linking `embedded_daemon.cpp` into the test target — its deps were already there). The F1 test hammers `isRunning()` from the test thread while the child exits, so it's a genuine regression test for the reap race. **The F2 test caught a real bug:** `start()`'s failure branch overwrote `startProcess()`'s precise `last_error_` ("…not executable or wrong architecture") with a generic "Failed to start dragonxd process" (because `setState(Error, …)` stores its message into `last_error_`), so the precise reason never reached `getLastError()`/the UI — **fixed** to preserve the detail (now also surfaced via the state callback / crash panel). Build-clean; `ctest` 1/1.
+
 - **F1** — ☑ landed: `isRunning()` (POSIX) now reads the atomic `state_` (predicate `Running || Stopping`) instead of calling `waitpid`, leaving `monitorProcess()` the sole reaper. Clean build (all targets link); `ctest` 1/1 passing. Not unit-testable — needs the manual `kill -SEGV` repro before release.
 - **F2** — ☑ landed: `startProcess()` (POSIX) now creates a `FD_CLOEXEC` self-pipe before `fork()`; the child writes `errno` to it on `execv` failure, the parent reads EOF-vs-errno and, on failure, reaps the zombie + sets a precise `last_error_` ("not executable or wrong architecture") + returns `false` (so `start()` no longer reports `Running` for a daemon that never started). Parent-side `setpgid` is now best-effort with a `DEBUG_LOGF` on failure. Clean build; `ctest` 1/1 passing. Not unit-testable — needs the manual non-executable / wrong-arch-binary repro before release.
 - **F8** — ☑ landed: `isLocalHost()` tightened to exact loopback via `isExactIPv4Loopback` (a `127.`-prefixed *hostname* like `127.evil.com` is no longer misclassified as local). `tryConnect()` now **refuses** a plaintext connection to a remote host instead of warn-and-proceeding — a local-network MITM can no longer capture `rpcuser:rpcpassword` — unless the user opts in with `rpcallowplaintext=1` in `DRAGONX.conf` (new `ConnectionConfig::allow_plaintext_remote` + `allowsPlaintextRemote()` policy). The refusal surfaces via status line + a one-time notification. New `testIsLocalHost` (12 assertions) + `testAllowsPlaintextRemote` (5). Clean build; `ctest` 1/1 passing. **Breaking — needs release notes; Settings-toggle UI deferred (see as-built note).**