v0.7.0

Features

• Added black-box cancellation contracts. A multi-turn scenario can request an initial
  non-terminal task with return_immediately: true, invoke the protocol-level cancel operation,
  and assert the returned task state, content, timing, files, data, and invariants.
• Added task persistence contracts through action: get_task, with optional bounded
  history_length. Task IDs and contexts flow between message, cancel, and retrieval turns without
  exposing transport-specific methods in the configuration.
• Added a2a-proof diff --against URL for running one selected contract against baseline and
  candidate deployments. Terminal and JSON output classify Agent Card and scenario outcomes as
  regressions, improvements, changed, or unchanged; the candidate contract result controls the
  exit status.
• Kept lifecycle behavior portable across JSON-RPC, HTTP+JSON, and gRPC. Streaming agents use a
  dedicated non-streaming client for the A2A return_immediately request while normal scenarios
  retain streaming state trajectories and first-event timing.

Security

• Applied the existing URL credential rejection, Agent Card origin checks, redirect policy,
  request headers, extensions, response bounds, and timeouts to lifecycle and candidate diff runs.
• Kept differential comparison at the contract-result layer instead of fetching or comparing
  untrusted remote resources; response file URLs remain passive and omitted from reports.

Documentation

• Added a complete cancellation-and-persistence contract and documented lifecycle ordering,
  missing-task behavior, history limits, diff classifications, and diff exit codes.
• Kept the README focused on first use and moved contract, assertion, lifecycle, and operational
  reference material into short topic guides.

Maintenance

• Added real lifecycle exchanges for every supported transport and a real CLI deployment diff;
  272 tests retain complete statement and branch coverage across the expanded surface.
• Added lifecycle configuration constraints to the generated JSON Schema and differential result
  classification to mutation testing, with 98.8% of 2,362 mutants killed.