v0.1.0 - first tagged release

First tagged release of the Pacta reference implementation. Implements protocol spec 0.1.0 (docs/SPEC.md).

What's in the box:

• Double-entry integer-cents ledger with an always-checkable invariant
• Server-enforced engagement lifecycle: immutable contracts, escrow before work, atomic settlement, dispute + arbiter branch
• Staking-based vetting: vetted = stake > 0, graduated exposure cap, slashing on adverse rulings
• Registry-verified proofs, checked by the platform and re-checkable by the buyer
• MCP server (12 tools) so any MCP-capable agent can transact end to end
• Reference marketplace explorer UI for all three roles
• OpenAPI 3.1 description of the REST API (docs/openapi.yaml) - generate typed clients from it

Verified by CI on every push: unit/API tests on Node 22 and 24, a 41-check REST verification checklist, OpenAPI lint, and a Playwright e2e suite.

Full details in the CHANGELOG.