v0.6.1

Completes the v0.6.0 doc-graph ingestion feature: the node now captures each repo's
doc-graph digest on a bare repo store, not just working-tree checkouts.

• Digests captured on bare repos. The node runs docgraph graph --json --ref <scanned ref> (docgraph v3.1.0's ref mode reads the committed ref from the git
  object store), so it no longer skips bare repos — the reference deployment's bare
  Forgejo store now populates docGraph digests and serves /repos/<id>/docgraph.json.
• Ref-consistency resolved. The digest now reflects the exact ref Mycelium
  scanned (the same ref used for the sidecar and recorded commit), on every repo —
  not the node's working-tree state. This closes the working-tree caveat of v0.6.0.
• Runtime requirement: capturing digests needs docgraph v3.1.0+ on the node's
  PATH. An older or absent docgraph degrades gracefully to no digest — the scan
  never fails.

No change to the graph.json / docGraph shape (schemaVersion 1); digests simply
start appearing where the store is bare.

Full Changelog: v0.6.0...v0.6.1