feat(ci): capture crash evidence as artifacts when a run wedges (T-436)

Closes the observability loop: the log + breadcrumb + watchdog files are now
collected by CI so a wedged run leaves downloadable evidence instead of
nothing.

- logDirectory(): CLIDE_LOG_DIR overrides the per-platform default, so CI can
  point the logs at an uploadable workspace dir (and tests at a temp dir).
  Now takes an injectable env map; tested.
- test_app.dart: when CLIDE_LOG_DIR is set, the testmode harness tees its
  logger to a FileLogSink + spawns the watchdog (off by default — normal
  run-testmode keeps the stderr-only path, no isolate). _say breadcrumbs each
  test into the file.
- conpty_orphan_probe.dart: with CLIDE_LOG_DIR set it passes a verbose PtyLog,
  so when soak-conpty-kill.ps1 force-kills the parent, the reader/waiter
  isolates' LAST crumb is fsynced to disk — naming what the wedged isolate was
  doing at the instant of death.
- bundle-smoke job: runs the real release app with CLIDE_LOG=debug +
  CLIDE_LOG_DIR, uploads clide-logs (watchdog heartbeat/sample + FileLogSink)
  in an always() step.
- windows-soak kill-probe job: sets CLIDE_LOG_DIR, uploads the FFI crumbs.

Coverage gate 95.08%.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

test/ipc/paths_test.dart

@@ -62,6 +62,12 @@ void main() {
       final home = Platform.environment['HOME']!;
       expect(logDirectory(), '$home/Library/Logs/clide');
     });
+
+    test('CLIDE_LOG_DIR overrides everything (CI artifact / test redirect)', () {
+      expect(logDirectory({'CLIDE_LOG_DIR': '/tmp/ci-logs'}), '/tmp/ci-logs');
+      // Empty override is ignored — falls through to the platform default.
+      expect(logDirectory({'CLIDE_LOG_DIR': '', 'XDG_STATE_HOME': '/x', 'HOME': '/h'}), isNot('/'));
+    });
   });
 
   group('fnv1a64Hex (T-126 cross-check)', () {