test(gateway): isolate plugin adapter imports and guard the anti-pattern

Fixes the xdist collision that broke CI on PR #17764, and structurally
prevents future plugin-adapter tests from reintroducing it.

Problem
-------
tests/gateway/test_teams.py (new in this PR) and tests/gateway/test_irc_adapter.py
(already on main) both followed the same anti-pattern:

  sys.path.insert(0, str(_REPO_ROOT / 'plugins' / 'platforms' / '<name>'))
  from adapter import <Adapter>

Every platform plugin ships its own adapter.py, so the bare
'from adapter import ...' races for sys.modules['adapter']. Whichever test
collected first in a given xdist worker won; the other crashed at
collection with ImportError, and the polluted sys.path cascaded into 19
unrelated test failures across tools/, hermes_cli/, and run_agent/ in the
same worker.

Fix
---
1. tests/gateway/_plugin_adapter_loader.py (new): shared helper
   load_plugin_adapter('<name>') that imports plugins/platforms/<name>/adapter.py
   via importlib.util under the unique module name plugin_adapter_<name>.
   Zero sys.path mutation, no possibility of collision.

2. tests/gateway/test_irc_adapter.py and tests/gateway/test_teams.py:
   migrated to the helper. All 'from adapter import ...' statements
   (including the ones inside test methods) are replaced with module-level
   attribute access on the loaded module.

3. tests/gateway/conftest.py: new pytest_configure guard that AST-scans
   every test_*.py under tests/gateway/ at session start and fails the
   run with a pointer to the helper if any test uses sys.path.insert into
   plugins/platforms/ OR a bare 'import adapter' / 'from adapter import'.
   Runs on the xdist controller only (skipped in workers). The next plugin
   adapter test that tries to reintroduce this pattern gets rejected at
   collection time with a clear remediation message.

4. scripts/release.py: add aamirjawaid@microsoft.com -> heyitsaamir to
   AUTHOR_MAP so the check-attribution workflow passes.

Validation
----------
scripts/run_tests.sh tests/gateway/                    4194 passed
scripts/run_tests.sh tests/gateway/test_{teams,irc}*   72 passed (both orderings)
scripts/run_tests.sh <11 prev-failing test files>      398 passed
Guard triggers correctly on both Path-operator and string-literal forms
of the anti-pattern.

scripts/release.py

@@ -58,6 +58,7 @@ AUTHOR_MAP = {
     "nbot@liizfq.top": "liizfq",
     "274096618+hermes-agent-dhabibi@users.noreply.github.com": "dhabibi",
     "dejie.guo@gmail.com": "JayGwod",
+    "aamirjawaid@microsoft.com": "heyitsaamir",
     "johnnncenaaa77@gmail.com": "johnncenae",
     "thomasjhon6666@gmail.com": "ThomassJonax",
     "focusflow.app.help@gmail.com": "yes999zc",