Python `list_sessions` docstring example uses a nonexistent `sessionId` attribute

[examon]

Summary

The Example: block in the docstring of CopilotClient.list_sessions (Python SDK) prints
session.sessionId, an attribute that does not exist on the objects the method returns.
Copying the documented example raises AttributeError.

list_sessions is annotated -> list[SessionMetadata] and builds its results with
SessionMetadata.from_dict(...). SessionMetadata is a dataclass that declares session_id;
sessionId exists only as the wire/JSON key, mapped to session_id inside
SessionMetadata.from_dict / to_dict. There is no sessionId property, alias, or
__getattr__ fallback, so the documented access can never succeed.

Where

python/copilot/client.py, in the CopilotClient.list_sessions docstring:

Example:
    >>> sessions = await client.list_sessions()
    >>> for session in sessions:
    ...     print(f"Session: {session.sessionId}")   # <- no such attribute

The returned type:

@dataclass
class SessionMetadata:
    """Metadata about a session"""

    session_id: str  # Session identifier
    start_time: datetime
    modified_time: datetime
    is_remote: bool
    summary: str | None = None
    context: SessionContext | None = None

Reproduction

No server, model, or credentials needed. The snippet constructs a SessionMetadata exactly the
way list_sessions does internally, then performs the documented access.

pip install github-copilot-sdk

from copilot.client import SessionMetadata

# The wire payload shape `list_sessions` feeds into SessionMetadata.from_dict(...)
wire = {
    "sessionId": "abc-123",
    "startTime": "2026-06-27T10:00:00Z",
    "modifiedTime": "2026-06-27T10:05:00Z",
    "isRemote": False,
    "summary": "demo session",
}

session = SessionMetadata.from_dict(wire)

# The attribute that actually exists:
print(f"[ok] session.session_id = {session.session_id}")

# The attribute the documented example tells you to read:
print(f"Session: {session.sessionId}")

Expected

The documented example prints each session's id, e.g. Session: abc-123.

Actual

[ok] session.session_id = abc-123
Traceback (most recent call last):
  File "repro.py", line 18, in <module>
    print(f"Session: {session.sessionId}")
                      ^^^^^^^^^^^^^^^^^
AttributeError: 'SessionMetadata' object has no attribute 'sessionId'. Did you mean: 'session_id'?

Notes

session_id is the correct spelling for this type, and it is what the rest of the SDK already
uses and asserts:

• the shipped dataclass field itself;
• the end-to-end tests, which assert session_id on exactly this return value
  (python/e2e/test_session_e2e.py);
• the generated sibling type SessionMetadataSnapshot, which also uses session_id;
• the sibling docstring for get_session_metadata, which documents the same object correctly as
  metadata.start_time.

Other bindings document this method with their own idiomatic spelling of the same wire field, so
the Python docstring is the only one affected: Go uses session.SessionID (go/client.go) and
.NET uses session.SessionId (dotnet/src/Client.cs).

Nothing in the repository executes these docstring examples (there is no --doctest-modules
setting and the docs-validation job only extracts Markdown under docs/), which is why lint,
type-checking, and the test suite all pass with the defect present.

The fix is to correct the documented attribute name. It is a docstring-only change with no
public API, behavior, or wire format impact.