…cker

Raise the runtime floor to Python 3.10 (verified on 3.10 and 3.12) and
modernize the HTTP toolchain:

  - python >=3.10,<4 (drop 3.9 from deps and CI matrix)
  - httpx >=0.28, pytest-httpx >=0.35, inflect >=7
  - dev: pytest >=8,<9, pytest-asyncio >=0.24,<2, pytest-cov <7

pytest-httpx >=0.35 (which pulls httpx 0.28) is the only path to httpx
0.28, and it forces the pytest/pytest-asyncio bumps transitively. Its
0.31+ API changes break the async mocker, so adapt it:

  - HTTPXMock now requires _HTTPXMockOptions; construct it with
    can_send_already_matched_responses=True so a single registered
    response answers the ConnectClient's retried requests. The strict
    assert_all_requests_were_expected default is kept, so an unmocked
    request fails the test.
  - reset() no longer performs assertions; call _assert_options()
    explicitly, gated by success, to keep failing on unrequested mocks.
  - match_content now serializes JSON with compact separators to match
    httpx 0.28's compact request-body serialization.

Mark test_execute_error_with_reason (native httpx_mock fixture, retries
on 500) with the matching httpx_mock options. All tests pass.

connect/client/fluent.py imported `Proxy` from httpx._config and
`get_environment_proxies` from httpx._utils. Both are private httpx APIs
that can change or vanish on any minor release, and the import happens at
module load, so a break would take down the whole client, not just proxy
support.

Reimplement the environment proxy discovery locally as
_get_environment_proxies() on top of stdlib urllib.request.getproxies()
and ipaddress, faithfully porting httpx 0.28's algorithm: http/https/all
schemes (normalizing bare host:port to a http:// URL) and NO_PROXY
handling for domains, IPv4, IPv6, localhost, explicit-scheme hosts, and
the NO_PROXY=* global bypass. Use the public httpx.Proxy instead of the
private one.

Add tests for this previously untested logic (scheme normalization, each
NO_PROXY host form, and the wildcard bypass). All 407 tests pass.

The install section still stated Python 3.9 as the minimum. Python 3.9
support was dropped on this branch (pyproject.toml now requires >=3.10),
so align the README with the actual requirement.

Address PR review on the httpx 0.28 / pytest-httpx 0.35 bump.

- match_content now mirrors httpx 0.28's request-body serialization
  exactly by adding ensure_ascii=False and allow_nan=False. Without
  them a non-ASCII match_body serialized to \uXXXX escapes while httpx
  sends raw UTF-8, so the mock silently failed to match.
- Pin an upper bound pytest-httpx >=0.35,<1. It is a runtime dependency
  (connect.client.testing ships the mocker and a pytest11 plugin) that
  relies on private pytest_httpx API (_HTTPXMockOptions, _assert_options),
  so an unbounded minor bump could break downstream test suites.
- Add test_create_match_non_ascii_body and test_unrequested_mock_fails
  to cover the non-ASCII matching and the reset() assertion path, which
  previously had no coverage.