Margins v0.4.0

Margins 0.4.0 makes fresh workspace setup agent-guided and retrieval-aware.

• margins setup provisions machine models and prints a minimal prompt for an
  agent to complete workspace setup from the intended base folder.
• margins guide workspace-setup embeds the complete setup workflow.
• margins scan now inspects folders, tags, wikilinks, frontmatter, page
  entities, and running logs before policy selection or margins init.
• Recall policy and model selection are Margins-owned under ~/.margins/;
  databases and target projections remain vault-local under .margins/recall/.
• Exact-phrase rescue and richer recall XML make retrieval results easier for
  agents to verify against real notes.

Official binaries include the complete recording and recall composition. The
public open-core source remains available for audit and extension; capture and
workspace contents remain local to the installed application.