fix theme picker integration test; one bake for build-time facts (T-116)

The test was awaiting services.commands.execute('theme.pick') whose
Future doesn't complete until the dialog is dismissed — deadlock.
Fire-and-forget around pumpAndSettle, then tap Cancel, then await
the original future. Also tear the widget tree down before
services.dispose() so listening widgets unsubscribe first.

Pre-existing layout overflow in the welcome _StatusLine surfaced
when running the test at narrower viewports. Switched to a whole-
row FittedBox(scaleDown) — uniform shrink on narrow screens, no-op
at standard widths.

User flagged the hardcoded 'clide 2.0.0-dev' string. Replaced with
one generated lib/src/build_info.g.dart (gitignored, regenerated
by `make gen-build-info` from pubspec.yaml + git short SHA + UTC
clock). The same target re-syncs assets/licenses.yaml self.version
in place — no second source. Every make build/run/test depends on
it implicitly. Welcome status line now reads `clideVersion`. Stale
fontSize literals in welcome_view swept to typography constants;
clideFontMeta=13, clideFontDialogTitle=16, clideFontWelcomeBanner=52
added to fill gaps in the scale.

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

lib/clide.dart

@@ -27,22 +27,8 @@ export 'src/ipc/schema_v1.dart';
 export 'src/panes/event_sink.dart';
 export 'src/panes/pane.dart' show Pane, PaneKind;
 
-/// Build-time-stamped version string.
-///
-/// The Makefile's `build` target passes `--define=clideVersion=…`,
-/// stamping `pubspec.yaml`'s `version:` plus the git short SHA and
-/// dirty marker.
-const clideVersion = String.fromEnvironment(
-  'clideVersion',
-  defaultValue: '2.0.0-dev',
-);
-
-const clideCommit = String.fromEnvironment(
-  'clideCommit',
-  defaultValue: 'unknown',
-);
-
-const clideDate = String.fromEnvironment(
-  'clideDate',
-  defaultValue: 'unknown',
-);
+// clideVersion / clideCommit / clideDate live in lib/src/build_info.g.dart,
+// regenerated by every `make` build/run/test target from pubspec.yaml +
+// git short SHA + current UTC time. See `gen-build-info` in the
+// Makefile.
+export 'src/build_info.g.dart' show clideVersion, clideCommit, clideDate;