ship the clide CLI on PATH (Epic A)

`make build`/`make install` now compile the C `clide` client by default
(clide-cli is a prereq of both), and `make install` places that binary at
$(INSTALL_DIR)/clide on Linux and macOS instead of symlinking the Flutter
GUI runner. The GUI still launches via its desktop entry / clide.app.
macOS install now delivers the CLI too; macOS uninstall removes it.

Adds a regression test asserting clideVersion (build_info.g.dart) stays
equal to pubspec.yaml version, so an agent keying off `clide version` is
never misled.

Closes T-210, T-211, T-213 (under T-209 / T-208 "Give Claude hands").

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

test/cli/clide_version_test.dart

@@ -0,0 +1,35 @@
+/// Regression guard for the `clide version` contract (T-213).
+///
+/// `clideVersion` (lib/src/build_info.g.dart, baked by gen-build-info)
+/// is what the dispatcher returns for `ping`/`version` and what the C
+/// client surfaces. An agent keys off `clide version`; if it ever drifts
+/// from pubspec.yaml `version:` — the single source of truth — that agent
+/// is misled. This test fails the moment the two diverge.
+library;
+
+import 'dart:io';
+
+import 'package:clide/clide.dart' show clideVersion;
+import 'package:test/test.dart';
+
+/// First `version:` entry in pubspec.yaml — mirrors the Makefile awk
+/// (`/^version:/ {gsub(/[" ]/,"",$2); print $2}`).
+String _pubspecVersion() {
+  final lines = File('pubspec.yaml').readAsLinesSync();
+  for (final line in lines) {
+    if (line.startsWith('version:')) {
+      return line.substring('version:'.length).replaceAll('"', '').trim();
+    }
+  }
+  fail('no `version:` line in pubspec.yaml');
+}
+
+void main() {
+  test('clideVersion matches pubspec.yaml version (T-213)', () {
+    expect(
+      clideVersion,
+      _pubspecVersion(),
+      reason: 'build_info.g.dart drifted from pubspec.yaml — run `make gen-build-info`',
+    );
+  });
+}