refactor: generic skills build system with auto-discovery (#8)

* refactor: generic skills build system with auto-discovery

- Rename postgres-best-practices-build → skills-build
- Add auto-discovery: scans skills/ for subdirectories with metadata.json
- Build/validate all skills or specific skill with -- argument
- Update root AGENTS.md and CONTRIBUTING.md with new structure
- No configuration needed to add new skills

Usage:
  npm run build                    # Build all skills
  npm run build -- skill-name      # Build specific skill
  npm run validate                 # Validate all skills

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix ci

* more generic impact levels

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

packages/skills-build/src/config.ts

@@ -0,0 +1,59 @@
+import { existsSync, readdirSync } from "node:fs";
+import { dirname, join } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = dirname(__filename);
+
+// Build package directory
+export const BUILD_DIR = join(__dirname, "..");
+
+// Skills root directory
+export const SKILLS_ROOT = join(BUILD_DIR, "../../skills");
+
+// Skill paths interface
+export interface SkillPaths {
+	name: string;
+	skillDir: string;
+	rulesDir: string;
+	agentsOutput: string;
+	metadataFile: string;
+}
+
+// Discover all valid skills (directories with metadata.json)
+export function discoverSkills(): string[] {
+	if (!existsSync(SKILLS_ROOT)) return [];
+
+	return readdirSync(SKILLS_ROOT, { withFileTypes: true })
+		.filter((d) => d.isDirectory())
+		.filter((d) => existsSync(join(SKILLS_ROOT, d.name, "metadata.json")))
+		.map((d) => d.name);
+}
+
+// Get paths for a specific skill
+export function getSkillPaths(skillName: string): SkillPaths {
+	const skillDir = join(SKILLS_ROOT, skillName);
+	return {
+		name: skillName,
+		skillDir,
+		rulesDir: join(skillDir, "rules"),
+		agentsOutput: join(skillDir, "AGENTS.md"),
+		metadataFile: join(skillDir, "metadata.json"),
+	};
+}
+
+// Validate skill exists
+export function validateSkillExists(skillName: string): boolean {
+	const paths = getSkillPaths(skillName);
+	return existsSync(paths.metadataFile);
+}
+
+// Valid impact levels in priority order
+export const IMPACT_LEVELS = [
+	"CRITICAL",
+	"HIGH",
+	"MEDIUM-HIGH",
+	"MEDIUM",
+	"LOW-MEDIUM",
+	"LOW",
+] as const;