distinguish a dev-tree clide from a packaged install (T-256)

CliInstaller.inspect() gains a devTree state: when `clide` on PATH resolves
to a dev-tree build artifact (native/<plat>/clide, the Makefile's
CLIDE_CLI_BIN output) it's classified separately from a packaged install
rather than silently treated as "installed". needsInstall stays false for a
dev build (it's intentional on a checkout, not a reinstall prompt), and the
launch-time check surfaces it as an info note. install() flags fromDevTree +
notes it in the result message when the copied source is a dev build.

Closes the last open child of the T-208 "give Claude hands" initiative.

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

lib/builtin/cli_install/src/extension.dart

@@ -48,6 +48,12 @@ class CliInstallExtension extends ClideExtension {
           'in PATH" to replace it.',
           title: 'clide CLI is stale',
         );
+      case CliInstallState.devTree:
+        ctx.notify.info(
+          '`clide` on your PATH is the dev-tree build, not a packaged install '
+          '— fine for development; rebuild it with `make clide-cli`.',
+          title: 'clide CLI: dev build',
+        );
       case CliInstallState.installed:
         break;
     }