refactor: rework integration events per maintainer review

- Rename hooks terminology to 'events' (events:, --events flag, events.py).
- Use snake_case names for canonical events consistent with spec-kit vocabulary.
- Fold event config adapters into integration classes via class attributes (CANONICAL_TO_NATIVE, events_config_file, events_format).
- Lift event command-script resolution to core 'specify event run' command.
- Split events sourcing from integration config writing.
- Support first-class Copilot CLI events JSON generation under '.github/hooks/speckit.json'.
- Rewrite and expand full test suite under 'tests/integrations/test_events.py'.

Assisted-by: opencode (model: litellm/gemini-3.5-flash, autonomous)

src/specify_cli/integrations/opencode/__init__.py

@@ -20,6 +20,15 @@ class OpencodeIntegration(MarkdownIntegration):
         "extension": ".md",
     }
 
+    CANONICAL_TO_NATIVE = {
+        "pre_tool_use": "tool.execute.before",
+        "post_tool_use": "tool.execute.after",
+        "session_start": "session.created",
+        "session_end": "session.deleted",
+    }
+    events_config_file = "opencode.json"
+    events_format = "ts-plugin"
+
     def build_exec_args(
         self,
         prompt: str,