docs(BA-5982): correct ExecutionData docstring (not all 'hooks')

Calling the three fields "execution-time hooks" was misleading —
``startup_command`` is the container's main entry command (replacing
the image CMD) and ``bootstrap_script`` is a pre-launch init script;
only ``callback_url`` is an actual event-callback hook. The previous
"user-supplied vs resolver-produced" split rationale was also wrong:
``environ`` on ``ModelRuntimeConfigData`` is just as user-supplied,
merged from preset / request / deployment-config sources.

Rewrite the class docstring to describe the three fields by what they
actually do (container entry command, pre-startup setup script,
lifecycle event webhook), and add per-field comments explaining the
``None`` semantics. Keep the sibling-of-ModelRuntimeConfigData framing,
restated as a packaging convenience for downstream consumers rather
than a lifecycle distinction that does not really exist.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: jopemachine

src/ai/backend/manager/data/deployment/types.py

@@ -890,18 +890,24 @@ class ModelMountConfigData:
 
 @dataclass
 class ExecutionData:
-    """Execution-time hooks frozen on the persisted revision.
-
-    Sibling of ``ModelRuntimeConfigData`` (which carries the runtime
-    variant + environ + inference runtime knobs). Split out because these
-    three fields have a different lifecycle: they are user-supplied
-    overrides layered on top of preset / deployment-config / model-
-    definition resolution, while runtime variant + environ are produced
-    by the resolver pipeline.
+    """Container-execution overrides frozen on the persisted revision:
+    what command runs in the model container, what setup script runs
+    before it, and where deployment lifecycle events get POSTed.
+
+    Sibling of ``ModelRuntimeConfigData`` (runtime variant / environ /
+    inference runtime knobs); kept separate so the schedulers and draft
+    builders can pass these straight to the kernel spec without picking
+    them out of the runtime config bag.
     """
 
+    # Replaces the image ``CMD`` when starting the model container.
+    # ``None`` keeps whatever the image baked in.
     startup_command: str | None
+    # Shell script run once at container startup, before
+    # ``startup_command``. ``None`` for revisions that do no extra setup.
     bootstrap_script: str | None
+    # Webhook the manager POSTs to on deployment lifecycle events
+    # (provisioning, ready, failure, …); ``None`` disables callbacks.
     callback_url: yarl.URL | None