chore(harness): run changed suites in CI

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

scripts/harness/validate.mjs

@@ -94,6 +94,40 @@ function runCommand(command) {
   };
 }
 
+function printSelection(selection) {
+  if (selection.suites.length === 0) {
+    process.stdout.write("[harness] No suites selected for the current diff.\n");
+
+    if (selection.unmatchedFiles.length > 0) {
+      process.stdout.write("[harness] Unmatched files:\n");
+
+      for (const filePath of selection.unmatchedFiles) {
+        process.stdout.write(`  - ${filePath}\n`);
+      }
+    }
+
+    return;
+  }
+
+  process.stdout.write("[harness] Selected suites from changed files:\n");
+
+  for (const suiteName of selection.suites) {
+    process.stdout.write(`- ${suiteName}\n`);
+
+    for (const reason of selection.reasons[suiteName] ?? []) {
+      process.stdout.write(`  - ${reason.file}: ${reason.reason}\n`);
+    }
+  }
+
+  if (selection.unmatchedFiles.length > 0) {
+    process.stdout.write("[harness] Unmatched files:\n");
+
+    for (const filePath of selection.unmatchedFiles) {
+      process.stdout.write(`  - ${filePath}\n`);
+    }
+  }
+}
+
 const options = parseArgs(process.argv.slice(2));
 
 if (options.list) {
@@ -128,6 +162,7 @@ const report = {
 
 if (selection) {
   report.selection = selection;
+  printSelection(selection);
 }
 
 for (const command of commands) {