fix(ci): docs:check-links groen — exclude docs/old/ + archiveer stale plans (#193)

CI faalde sinds #191 (docs cleanup) op pre-existing broken links:
- docs/old/ bevat archief-docs met by-design stale paden
- docs/plans/PBI-79*, M9*, M11* hadden geprojecteerde paden naar
  ../backlog/index.md (verplaatst naar docs/old/backlog/) en naar
  app-bestanden die nooit met de juiste relatieve prefix waren geschreven
- docs/adr/0000* verwees naar docs-restructure-ai-lookup.md (verplaatst)
- docs/glossary.md verwees naar /docs/backlog/index.md (verplaatst)

Fixes:
- scripts/check-doc-links.mjs: skip docs/old/ recursief
- Move docs/plans/{PBI-79,M9,M11}*.md → docs/old/plans/ (allemaal merged PBIs;
  plans waren historisch)
- docs/adr/0000-record-architecture-decisions.md: update pad naar archief
- docs/glossary.md: verwijder dode "backlog index"-link

Verificatie: `npm run docs:check-links` → ✓ All doc links valid (105 files)

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

scripts/check-doc-links.mjs

@@ -14,8 +14,16 @@ import { fileURLToPath } from 'url';
 const __dirname = dirname(fileURLToPath(import.meta.url));
 const ROOT = resolve(__dirname, '..');
 
+// Directories under docs/ that are archived and may contain stale links by design.
+// Their original-as-written paths are kept for historical reference, but the
+// targets have since moved/been deleted. Skip them from link-checking.
+const EXCLUDE_DIRS = new Set([
+  resolve(__dirname, '..', 'docs', 'old'),
+]);
+
 // Collect all .md files under a directory recursively
 function collectMd(dir) {
+  if (EXCLUDE_DIRS.has(dir)) return [];
   const results = [];
   for (const entry of readdirSync(dir)) {
     const full = resolve(dir, entry);