Canvas & Extensions authoring API: out-of-scope for 1.0.0 GA #121

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Canvas & Extensions: declare out-of-scope for 1.0.0 GA (or implement post-GA)

Found during the GA upstream parity audit (Phase 1).

The Node.js SDK exposes a Canvas / Extensions authoring surface that this SDK does not implement:

• Session config fields for canvas/extension registration.
• A session getter for canvas state.
• A canvas authoring API.

What this SDK does already do: the generated wire layer parses and coerces the
related session events (session.canvas.opened, session.canvas.registry_changed,
session.extensions.attachments_pushed), and they are now in the public event-types
set (see the F2 fix). So canvas/extension activity is observable even though the
authoring API is absent.

Decision for GA

Treat the canvas/extensions authoring API as out-of-scope for 1.0.0 GA and
document it as a known limitation (the observable events remain supported). Revisit
implementing the authoring surface post-GA based on demand.

Upstream references (tag v1.0.0-beta.12):

• nodejs/src/types.ts — canvas/extension config fields
• nodejs/src/session.ts — canvas getter

Severity: post-ga.