lib: idea-code generator + plan_md yaml-frontmatter parser (M12 T-494)

- lib/idea-code.ts: pure formatIdeaCode helper (client-safe, no prisma)
- lib/idea-code-server.ts: atomic nextIdeaCode via Prisma row-lock,
  accepts optional TransactionClient for combining with idea.create
- lib/idea-plan-parser.ts: parsePlanMd extracts ---yaml---/body, runs
  yaml.parse + ideaPlanMdFrontmatterSchema, returns line-info on failure;
  CRLF-tolerant
- adds yaml@^2.8.4 dependency
- 8 unit tests (parser happy/missing/yaml-error/zod-error/empty-stories/CRLF;
  formatIdeaCode pad-3 + overflow)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/idea-code-server.ts

@@ -0,0 +1,26 @@
+// Atomic per-user idea-code generator (DB-side).
+// Schema: User.idea_code_counter Int @default(0) — increment-and-return via
+// Prisma `update` (which acquires a row-lock for the duration of the
+// transaction; concurrent calls serialize). Format: "IDEA-001", "IDEA-002", …
+//
+// Concurrency: vertrouwt op Postgres row-locking binnen Prisma `update`.
+// Geen aparte $transaction nodig voor enkelvoudige update — de update is
+// atomisch op één rij. Voor combineren met een idea.create wordt
+// nextIdeaCode aangeroepen binnen de bredere $transaction van de caller.
+
+import { prisma } from '@/lib/prisma'
+import { formatIdeaCode } from '@/lib/idea-code'
+
+import type { Prisma } from '@prisma/client'
+
+export async function nextIdeaCode(
+  userId: string,
+  client: Prisma.TransactionClient | typeof prisma = prisma,
+): Promise<string> {
+  const u = await client.user.update({
+    where: { id: userId },
+    data: { idea_code_counter: { increment: 1 } },
+    select: { idea_code_counter: true },
+  })
+  return formatIdeaCode(u.idea_code_counter)
+}

lib/idea-code.ts

@@ -0,0 +1,8 @@
+// Pure helpers voor IDEA-codes. Geen DB-imports — daarom client-safe.
+// De DB-mutating nextIdeaCode staat in lib/idea-code-server.ts.
+
+const PAD = 3 // "IDEA-001". Bumps to 4 digits at counter 1000 organically.
+
+export function formatIdeaCode(n: number): string {
+  return `IDEA-${String(n).padStart(PAD, '0')}`
+}

lib/idea-plan-parser.ts

@@ -0,0 +1,73 @@
+// Parser voor de plan_md die make-plan-job produceert.
+// Format: yaml-frontmatter (structuur, parseerbaar) + markdown-body (vrije
+// reasoning). Frontmatter wordt gevalideerd via ideaPlanMdFrontmatterSchema.
+//
+// Wordt zowel door de server-action materializeIdeaPlanAction als door de
+// MCP-tool update_idea_plan_md gebruikt. Synchroon — geen LLM-call.
+//
+// Zie docs/plans/M12-ideas.md "Plan-md formaat A" voor het format-voorbeeld.
+
+import { parse as parseYaml, YAMLParseError } from 'yaml'
+import {
+  ideaPlanMdFrontmatterSchema,
+  type IdeaPlanFrontmatter,
+} from '@/lib/schemas/idea'
+
+export type PlanParseError = { line?: number; message: string }
+
+export type PlanParseResult =
+  | { ok: true; plan: IdeaPlanFrontmatter; body: string }
+  | { ok: false; errors: PlanParseError[] }
+
+const FRONTMATTER_RE = /^---\r?\n([\s\S]*?)\r?\n---\r?\n?([\s\S]*)$/
+
+export function parsePlanMd(md: string): PlanParseResult {
+  const match = md.match(FRONTMATTER_RE)
+  if (!match) {
+    return {
+      ok: false,
+      errors: [
+        {
+          line: 1,
+          message:
+            'Plan ontbreekt yaml-frontmatter. Verwacht eerste regel: ---',
+        },
+      ],
+    }
+  }
+
+  const [, frontmatterRaw, body] = match
+
+  let parsed: unknown
+  try {
+    parsed = parseYaml(frontmatterRaw)
+  } catch (err) {
+    if (err instanceof YAMLParseError) {
+      return {
+        ok: false,
+        errors: [
+          {
+            line: err.linePos?.[0]?.line,
+            message: err.message,
+          },
+        ],
+      }
+    }
+    return {
+      ok: false,
+      errors: [{ message: err instanceof Error ? err.message : String(err) }],
+    }
+  }
+
+  const validation = ideaPlanMdFrontmatterSchema.safeParse(parsed)
+  if (!validation.success) {
+    return {
+      ok: false,
+      errors: validation.error.issues.map((iss) => ({
+        message: `${iss.path.join('.') || '<root>'}: ${iss.message}`,
+      })),
+    }
+  }
+
+  return { ok: true, plan: validation.data, body: body.trimStart() }
+}