feat(hitl): add create_hitl_request — paired SDK release for ADK plugin v1

[saurabhjain1592]

Summary

Adds client.create_hitl_request(...) for explicit creation of HITL
approval rows via POST /api/v1/hitl/queue. This is the paired SDK
release that unblocks the Google ADK plugin v1 fixup
(getaxonflow/axonflow-enterprise#2410) — without this method, the
plugin's HITL polling path can't actually enqueue a row to poll.

Part of the cross-SDK parity sweep tracked at
getaxonflow/axonflow-enterprise#2421 (umbrella) — sister PRs for
TypeScript / Go / Java land in the same v8.1.0 train.

Why now

The platform's POST /api/v1/hitl/queue endpoint has existed since
v6.x (handler at platform/agent/hitl/handler.go:177). The Python SDK
exposed the read + review surface (get_hitl_request,
approve_hitl_request, reject_hitl_request) but had no create_*
counterpart. Agent-framework plugins detecting require_approval from
pre_check / check_tool_input need to create the row themselves
before polling — the gate endpoints set BlockReason="require_approval"
and mint a correlation ID, but do not call CreateApprovalRequest
themselves.

Changes

• axonflow/client.py — async create_hitl_request(request) -> HITLApprovalRequest
  • sync wrapper on SyncAxonFlow.
• axonflow/hitl.py — HITLCreateInput Pydantic model mirroring
  platform/agent/hitl/handler.go:86 CreateRequestInput. Required
  fields: client_id, original_query, request_type. Optional
  fields cover policy attribution, severity, compliance framework,
  expiry override, and the new notify_url field
  (getaxonflow/axonflow-enterprise#2419 platform companion). The
  notify_url field also surfaces on HITLApprovalRequest so callers
  can read back the value the platform stored.
• tests/test_hitl.py — 4 new tests covering: full-fields create,
  minimal required-fields create, 401 → AuthenticationError,
  connection failure → ConnectionError.
• runtime-e2e/create_hitl_request/ — real-stack proof: real httpx
  transport against a socketserver.TCPServer mimicking the platform
  handler. Asserts the wire body carries every required field +
  notify_url, and the response envelope parses back into a populated
  HITLApprovalRequest. Satisfies the Runtime E2E required for user-facing changes DoD gate.
• tests/test_telemetry_short_lived.py — drive-by stabilization
  (orthogonal): the subprocess test was silently failing whenever the
  global stamp file at ~/Library/Caches/axonflow/python-telemetry-last-sent
  already existed from a prior test run, because the heartbeat gate's
  7-day delivered-cadence short-circuits the ping. Isolated via
  tempfile.TemporaryDirectory + HOME/XDG_CACHE_HOME/LOCALAPPDATA
  env overrides so the per-platform stamp resolver lands in an empty
  directory. Picked up in this PR because it failed on a clean run of
  the full suite — HARD RULE fix: datetime parsing fails with nanosecond timestamps #1 (no "pre-existing issues").
• CHANGELOG.md + pyproject.toml + _version.py — bump 8.1.0 →
  8.2.0 (additive; no breaking changes).

Test plan

• pytest tests/test_hitl.py -v green (29 tests, including 4 new)
• pytest tests/ green (992 passed, 29 skipped — full suite)
• python runtime-e2e/create_hitl_request/test.py PASS
• ruff check . clean
• No regression on existing HITL test cases

How the new method is consumed

The Google ADK plugin's before_model_callback / before_tool_callback
detects block_reason == "require_approval", calls
client.create_hitl_request(...) with policy attribution + original
query, then polls client.get_hitl_request(returned.request_id) until
the row reaches a terminal state. See the linked plugin PR for the
end-to-end shape.

Refs getaxonflow/axonflow-enterprise#2421 (umbrella),
getaxonflow/axonflow-enterprise#2419 (notify_url platform companion),
getaxonflow/axonflow-enterprise#2393 (driving epic),
getaxonflow/axonflow-enterprise#2410 (ADK plugin v1 fixup)