Port pydantic-ai's A2A integration tests + wire CI to run them

[dsfaccini]

Summary

Brings the A2A integration tests over from pydantic/pydantic-ai's tests/test_a2a.py so the fasta2a.pydantic_ai bridge has real CI coverage upstream. After this lands, pydantic-ai can safely drop its in-tree tests/test_a2a.py in the v2-exec PR (companion: pydantic/pydantic-ai#5426 merged 2026-05-15, follow-up v2-exec PR pending).

What's covered

tests/test_pydantic_ai.py (11 tests, ported verbatim — snapshots transferred unchanged because the bridge code is identical):

• Pydantic model output with JSON schema metadata
• Lifespan-required runtime error
• Text / file-URI / file-bytes / data Part round-trips
• Error handling (worker raises → task state='failed')
• Multi-task context sharing (context_id accumulates message history)
• Thinking-response serialization
• History splicing before worker pickup
• Multi-message conversations across tasks/send

CI changes

.github/workflows/main.yml:

• Trigger expanded to release/** branches (so this branch's CI fires)
• Install step adds --extra pydantic-ai; the extra is marker-gated to Python 3.10+, so on the 3.9 matrix row it resolves to nothing and the test file short-circuits via pytest.importorskip('pydantic_ai')

Dev deps

• anyio (explicit; previously transitive)
• dirty-equals (for IsStr / IsDatetime / IsNow matchers used in inline-snapshot snapshots)
• tests/assets/kiwi.jpg for the file-content test (~100KB)

Verification

scripts/check clean (ruff format/check, pyright 0/0/0 with file-level reportUnknownVariableType / reportUnknownArgumentType suppression — the bridge raises ImportError when pydantic-ai is missing so pyright sees an Unknown branch on every call); scripts/test 16/16 pass (5 existing + 11 new); coverage on fasta2a/pydantic_ai/_bridge.py jumps from 0% to 89%.

[echarles]

Thx @dsfaccini for opening this, that will help to have better coverage indeed

CI is failing with lint errors https://github.com/datalayer/fasta2a/actions/runs/25979237907/job/76911386271?pr=57

   |
help: Remove unused `noqa` directive

Found 9 errors.
[*] 9 fixable with the `--fix` option.
Error: Process completed with exit code 1.

[dsfaccini]

hey @echarles sorry I was working on pydantic-ai v2 for the past week, so just got back to this. gonna merge this one, then update the PR I have against main

[echarles]

Tx @dsfaccini - what is the goal of the release/0.6 branch vs the main branch?

[dsfaccini]

hey @echarles , the release/0.6 branch was the branch used to do the 0.6.0 release

after that release in October last year, 6 commits with breaking changes were made in march that stayed unreleased

in order for me to migrate the pydantic ai integration into here and release it, so we can link it and users can use it immediately, I had to either merge the pyai bridge onto main and release a 0.7.0 with breaking changes, or merge it onto release/0.6 and to release it immediately and breaking change-free as 0.6.1, which is what I did

#55 is green and folds all changes done in release/0.6 onto main

now I just need to migrate the existing issue in the pydantic ai repo onto here (3 issues)

[echarles]

Thx for the explanation. I will review #55 asap