refactor(extensions): simplify lib helpers, tool registration and kit-doctor

Behavior-preserving cleanups:
- extract shared resolveBaseUrl helper for jira/confluence base-URL logic
- extract shared registerTool helper; port jira/gitlab/confluence tools to it
- make scanSecrets declarative (filter/map)
- collapse ok/warn pair into status() and drop double existsSync in kit-doctor

Typecheck clean; npm test 71 PASS, 0 FAIL.

extensions/lib/secrets.ts

@@ -29,12 +29,8 @@ export const SECRET_PATTERNS: SecretPattern[] = [
 /** Return the names of secret patterns found in `text` (empty if none). */
 export function scanSecrets(text: string): string[] {
 	if (!text) return [];
-	const hits: string[] = [];
-	for (const p of SECRET_PATTERNS) {
-		// Use a non-stateful copy (no global flag) to avoid lastIndex surprises.
-		if (p.re.test(text)) hits.push(p.name);
-	}
-	return hits;
+	// No pattern carries the /g flag, so `test` stays stateless and order is preserved.
+	return SECRET_PATTERNS.filter((p) => p.re.test(text)).map((p) => p.name);
 }
 
 /** Replace every secret occurrence with a labelled placeholder. */