fix: send stable user-agent from the Python SDK

[ryanmcmillan]

Summary

• centralize the SDK version/user-agent metadata
• send an explicit User-Agent from both the sync urllib client and async httpx client
• add coverage for sync and async header propagation

Why

Hosted SDK calls from a fresh controller were getting blocked by Cloudflare with error 1010 because the stdlib urllib client was not sending an explicit user agent.

Validation

• cd /Users/openclaw/projects/delega-python && PYTHONPATH=src python3 -m unittest
• installed this branch on the fresh controller CT and reran /root/work/delega-tests/sdk/sdk-hosted.sh -> 14/14 pass

[greptile-apps]

Greptile Summary

This PR fixes a Cloudflare 1010 error that was blocking Python SDK calls from fresh controllers by centralizing version metadata into a new _version.py module and explicitly setting a User-Agent header on both the synchronous urllib-based client and the async httpx client. The fix is minimal, well-targeted, and adds test coverage for header propagation in both transport layers.\n\nKey changes:\n- New src/delega/_version.py establishes a single source of truth for __version__ and the USER_AGENT string (delega-python/0.1.2).\n- __init__.py now re-exports __version__ from _version.py rather than defining it inline — backwards compatible with from delega import __version__.\n- _http.py and async_client.py both import USER_AGENT and inject it into their respective header dicts.\n- tests/test_client.py adds test_auth_header assertion for the sync User-agent and a new test_async_client_sets_user_agent test that mocks _require_httpx to verify the httpx.AsyncClient is constructed with the correct User-Agent kwarg.

Confidence Score: 5/5

Safe to merge — fixes a concrete production outage with a small, well-tested, backwards-compatible change.

The change is minimal and surgical: one new module, two one-line header additions, and two new tests that directly verify the fix. No public API surface changes, version is consistent, and the root cause (missing User-Agent blocked by Cloudflare 1010) is directly addressed. End-to-end validation was reported as 14/14 passing.

No files require special attention.

Important Files Changed

Filename	Overview
src/delega/_version.py	New file centralizing __version__ and USER_AGENT; clean and correct single source of truth.
src/delega/init.py	Replaces inline __version__ assignment with import from _version.py; backwards-compatible re-export.
src/delega/_http.py	Adds User-Agent: delega-python/0.1.2 to sync urllib request headers; straightforward and correct.
src/delega/async_client.py	Adds User-Agent to the httpx.AsyncClient header dict; correctly placed so all async requests inherit it.
tests/test_client.py	Extends existing header test for sync User-agent and adds new async test via _require_httpx mock; both tests are well-structured.

_{Reviews (1): Last reviewed commit: "fix: send stable user agent from python ..." | Re-trigger Greptile}