Reconcile pytest config/hooks with the real tests/ layout; handle root test_*.py scripts

[AndreaV-Lsi]

Context

Issue #1 (the input-serialization PR) introduced a real tests/ directory
(test_inputs.py, test_update_readonly.py, test_integration_smoke.py), added
[tool.pytest.ini_options] (asyncio_mode = "auto", testpaths = ["tests"]), and pytest-asyncio.
So the original "there is no tests/ dir" gap is partly closed. This issue covers the remaining
reconciliation.

Problem

• .claude/hooks.json runs pytest tests/ guarded on edits to openproject-mcp.py / src/tools/
  — the path guard predates the modular layout (overlaps with the .claude tooling issue).
• Root-level test_*.py (test_tools.py, test_news_tools.py, test_news_validation.py,
  test_news_integration.py) are manual scripts run as python test_*.py, outside
  testpaths=["tests"], so they are not part of the suite. test_tools.py also relies on awaiting
  a @mcp.tool object directly, which doesn't work on the 2.x API (the tool is a FunctionTool;
  the awaitable is .fn).

Scope

• Adjust .claude/hooks.json (and confirm config.json testCommand) so the pytest invocation
  matches the real tests/ layout.
• Decide per root script: migrate into tests/ as proper pytest (network-free, mocked) or
  clearly document it as a manual live script (and fix the .fn await issue in test_tools.py if
  kept).

Out of scope

• The input-handling tests already added in Make wrapped Pydantic input tools robust to MCP clients that serialize object args as JSON strings #1.
• Broad new test coverage beyond reconciling what exists.

Acceptance criteria

• uv run pytest is green and is the single source of automated tests.
• The .claude hooks' pytest command actually runs against tests/.
• Root test_*.py scripts are either pytest-ified under tests/ or documented as manual.

Type: tests/infra. Depends on / overlaps: #1 and the .claude tooling issue. Label: backlog.