Add frontend integration checklist and docs-drift guard

PLUGIN-QUICKSTART Step 7 is now a concrete 7-item checklist (view
conventions, route auto-discovery + ADR-009 gating meta, api client
shape, nav/report hooks, settings auto-nesting, verification).

New tests/test_docs_contract.py introspects BasePlugin and fails CI when
a public hook is missing from PLUGIN-HOOKS.md or the documented contract
version drifts - it immediately caught two undocumented hooks
(get_provisioning_note, get_config_schema), now documented.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/test_docs_contract.py

@@ -0,0 +1,61 @@
+"""Docs-drift guards: docs/PLUGIN-HOOKS.md must track the live contract.
+
+PLUGIN-HOOKS.md is the canonical plugin-author reference. These tests fail
+when the contract surface moves without the doc: a version bump that skips
+the doc's version example, or a new/renamed BasePlugin hook with no doc
+mention. Keeping this structural (not manual review) is what lets sister
+sites trust the doc.
+"""
+
+import inspect
+from pathlib import Path
+
+from shopdb import __contract_version__
+from shopdb.plugins.base import BasePlugin
+
+HOOKS_DOC = Path(__file__).resolve().parent.parent / 'docs' / 'PLUGIN-HOOKS.md'
+
+
+def test_hooks_doc_exists():
+    assert HOOKS_DOC.exists(), 'docs/PLUGIN-HOOKS.md is missing'
+
+
+def test_hooks_doc_declares_current_contract_version():
+    """The doc's version example must match the live __contract_version__."""
+    text = HOOKS_DOC.read_text()
+    expected = f"__contract_version__ = '{__contract_version__}'"
+    assert expected in text, (
+        f'docs/PLUGIN-HOOKS.md version example is stale: expected {expected}. '
+        f'Update the "Contract version" section when bumping the contract.'
+    )
+
+
+def test_every_public_hook_is_documented():
+    """Every public BasePlugin method must be mentioned in the doc."""
+    text = HOOKS_DOC.read_text()
+    hooks = [
+        name for name, member in inspect.getmembers(
+            BasePlugin, predicate=inspect.isfunction)
+        if not name.startswith('_')
+    ]
+    assert hooks, 'No public hooks found on BasePlugin (introspection broke?)'
+    missing = [hook for hook in hooks if hook not in text]
+    assert not missing, (
+        'BasePlugin hooks missing from docs/PLUGIN-HOOKS.md: '
+        + ', '.join(missing)
+        + '. Add a section (or mention) for each before shipping the hook.'
+    )
+
+
+def test_doc_does_not_reference_removed_hooks():
+    """Hooks removed from the contract must not be documented as current.
+
+    They may appear in "Removed" notes; this only guards section headings.
+    """
+    text = HOOKS_DOC.read_text()
+    for removed in ('get_searchable_fields', 'get_event_handlers'):
+        assert not hasattr(BasePlugin, removed)
+        assert f'### `{removed}' not in text, (
+            f'{removed} was removed from the contract but still has a '
+            f'section heading in docs/PLUGIN-HOOKS.md'
+        )