chore(docs): prune internal planning/spec artifacts + sync i18n CHANGELOG to 3.8.24

- Remove internal quality-gate planning docs (PLANO-*, RELATORIO-*),
  openspec/superpowers/spec working notes, and a stale fixes doc that
  should not ship with the release.
- Drop the getting-started glob from the fumadocs source config.
- Add the [3.8.24] section stub to the 41 i18n CHANGELOG mirrors so the
  docs-sync gate is consistent (the EN CHANGELOG already had it).

.source/source.config.mjs

@@ -4,7 +4,6 @@ var docs = defineDocs({
   dir: "docs",
   docs: {
     files: [
-      "./getting-started/**/*.md",
       "./architecture/**/*.md",
       "./guides/**/*.md",
       "./reference/**/*.md",