Pictovap 0.12.0

Pictovap 0.12.0

Pictovap 0.12.0 makes standalone adapter contribution a complete, repeatable
package workflow instead of a code-only scaffold.

What changed

• pictovap scaffold provider <name> and pictovap scaffold cms <name> now
  generate a Makefile and a minimal GitHub Actions test workflow.
• Generated adapters explicitly implement the public ImageSourceAdapter or
  CMSAdapter protocol and target the current pictovap>=0.11.0 contract.
• pictovap.testing.sample_candidate() provides a deterministic candidate
  fixture for provider response-mapping tests.
• Provider starter tests include the complete candidate shape and the
  credential-free contract path.

Upgrade path

Existing adapter packages do not need to change immediately. New packages
should regenerate their starter files or update their Pictovap dependency to
>=0.11.0, then run make check and pictovap adapter check --exercise.