Remove the docs migration shims once rossoctl/rossoctl#2530 has landed

[Ibrahim2595]

Raised by @esnible in review of #120: two deliberately temporary pieces exist only to make #120 safe to merge in either order relative to rossoctl/rossoctl#2530. Both are commented as temporary. Without a tracking issue they will outlive their purpose.

1. The MIGRATION WINDOW block in scripts/sync-docs.sh

It synthesises a minimal docs/index.md when upstream does not supply one. The restructured docs supply docs/index.md with slug: /, so the block becomes a no-op the moment #2530 lands.

if [[ ! -f "$DEST/index.md" ]]; then
  printf -- '---\ntitle: Rossoctl documentation\nslug: /\n---\n\nChoose a section from the sidebar.\n' \
    > "$DEST/index.md"
  echo "==> synthesised docs/index.md (upstream does not provide one yet)."
fi

To remove: delete the block. Then confirm /docs/dev/ still resolves — it should, from the upstream docs/index.md.

2. The legacy entries in the exclude array in docusaurus.config.ts

// --- Legacy locations, pre-restructure. ---
'superpowers/**',
'authbridge/**',
'automation-health.md',

#2530 moves that content under docs/_internal/, which the default '**/_*/**' pattern already excludes. The three entries then match nothing.

To remove: delete only those three lines. Keep the four Docusaurus defaults above them — '**/_*.{js,jsx,ts,tsx,md,mdx}', '**/_*/**', '**/*.test.{js,jsx,ts,tsx}', '**/__tests__/**'. Providing exclude replaces the defaults rather than extending them, so removing those four silently publishes docs/_internal/ and fails the build on its repo-relative image links. The comment in the file says this; it is the reason the array exists at all.

Verification after removal

npm run sync-docs && npm run build

Expect: build succeeds, /docs/dev/ resolves, and no route under /docs/dev/_internal/ or /docs/dev/superpowers/ is generated.

Blocked on

rossoctl/rossoctl#2530