fix: add transport retries to hosted_api_client to handle SQLite lock contention

[devin-ai-integration]

Fixes intermittent httpx.ReadError failures in tests using hosted_api_client, such as test_get_runs_in_queue_concurrency_limit_and_limit[1].

Root cause: The hosted_api_client fixture connects to a uvicorn server running in a subprocess that shares the same SQLite database as the test process. During parallel test execution (pytest-xdist), SQLite lock contention (database is locked) can cause the server's error handler to close the HTTP connection before the response is fully sent, resulting in httpx.ReadError on the client side.

Fix: Add httpx.AsyncHTTPTransport(retries=3) to the hosted_api_client fixture. This uses httpx's built-in transport retry mechanism, which retries only on connection-level errors (e.g., ReadError, ConnectError) — not on HTTP error responses (4xx/5xx). On retry, httpx establishes a new connection, recovering from the broken one.

This is a broader fix that addresses the issue for all tests using hosted_api_client rather than switching individual tests to ephemeral_client_with_lifespan.

Important review considerations

• Scope: This affects all ~160 test references using hosted_api_client across many test files. Transport retries should be safe since they only fire on connection-level failures, but worth considering if any tests intentionally validate connection behavior.
• Non-idempotent requests: If a POST request is processed by the server but the connection breaks before the response, the retry will re-send the POST, potentially causing a duplicate/conflict error instead of a ReadError.

Checklist

• This pull request references any related issue by including "closes <link to issue>"
  • This fixes a flaky test observed in workflow run #23067743779; no issue filed.
• If this pull request adds new functionality, it includes unit tests that cover the changes
• If this pull request removes docs files, it includes redirect settings in mint.json.
• If this pull request adds functions or classes, it includes helpful docstrings.

Link to Devin session: https://app.devin.ai/sessions/62533fe09ad943fa936cf77f7de1abcb
Requested by: bot_apk (apk@cognition.ai)

[devin-ai-integration]

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