fix(core): disable canvas provider group to avoid OHOS startup panic

[SWangHash]

The OHOS target cannot compile the canvas-runtime feature (oxc dependency). The core.canvas provider group is statically referenced by the product capability assembly and shared coding mode tools, so when canvas-runtime is disabled materialize_tool returns None for the canvas tools and create_product_tool_registry_from_plan panics at materialization.rs:89 on startup.

Comment out the Canvas capability pack and the shared coding mode append_provider_group_tools call for core.canvas so the provider group is never requested. This is a temporary measure until canvas-runtime can be conditionally enabled per target.

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