feat: A2A Agent Card schema and skill definitions (Phase 1)

[Copilot]

Adds A2A (Agent-to-Agent) protocol discoverability to Darwin Agentic Cloud — Phase 1: Agent Card schema and skill definitions.

Changes

• darwin/agenticcloud/a2a/agent_card.py — Pydantic models matching A2A v0.3.0+ Agent Card spec: AgentCard, AgentProvider, AgentCapabilities, AgentSkill
• darwin/agenticcloud/a2a/skills.py — Three core skill definitions (darwin.run, darwin.verify, darwin.identity) with full metadata, I/O modes, tags, and example request/response pairs. Includes get_agent_card() builder that reads version dynamically from darwin.agenticcloud.__version__
• tests/test_a2a_agent_card.py — 30 tests: schema compliance, field types, round-trip serialization, skill validation, no extra fields outside spec

Usage

from darwin.agenticcloud.a2a import get_agent_card

card = get_agent_card(url="https://darwin-agentic-cloud.fly.dev")
print(card.model_dump_json(indent=2))
# → valid /.well-known/agent-card.json content

Phase 2 (well-known URI endpoint on the FastAPI server) builds on this directly.

[vje013]

@copilot can you find the fix to the Lint test that I wrote into your memory? If so, can you apply next cycle?

[Copilot]

@copilot can you find the fix to the Lint test that I wrote into your memory? If so, can you apply next cycle?

I don't have a stored memory about this specific fix, but I identified the issue from the CI logs: ruff format --check was failing on tests/test_a2a_agent_card.py. Applied ruff format to fix it in commit 8441b33.

[vje013]

LGTM