v0.10.0

Added

• pgsquash validate-external for applying a migration path to a caller-owned
  empty PostgreSQL database, capturing a portable catalog snapshot, and
  comparing a second build against it. The command refuses non-empty databases,
  supports DSNs through an environment variable, and emits the stable
  pgsquash.external-validation.v1 JSON contract.
• Public catalog snapshot types and comparison helpers in pkg/validation.
• Catalog signatures for sequences, custom types and domains, relation and
  function ownership, row-security flags, policy roles, grants, and comments.

Changed

• Migration execution now honors context cancellation for compatibility SQL and
  every migration statement.
• CLI diagnostics use stderr so JSON output on stdout remains machine-readable.
• Release automation now publishes only native GitHub archives and checksums;
  obsolete Homebrew and container-registry publication paths were removed.
• Project documentation now describes the engine as a standalone OSS component
  and documents CapyDB-managed validation.

Removed

• The unused GitHub App/webhook package and its authentication dependencies.
• The managed subscription feature catalog and features CLI command; these
  described the retired hosted product rather than an OSS engine capability.
• Archived CapySquash platform manifests, Docker publishing, and self-analysis
  workflows from the engine repository.