fix: In custom component builder page, we shouldn't show "last event" / "last run" section of nodes

[cursor]

Summary

In the custom component builder page, there are no events or executions, so the "last event" / "last run" sections on nodes should not be shown.

Changes

• web_src/src/pages/custom-component/index.tsx: Simplified getBlockType to always return "component" type in the builder. Previously, merge components mapped to the "merge" block type, which used MergeComponent with its own empty state rendering that couldn't be suppressed. By using "component" type for all nodes, they all render through ComponentBase where includeEmptyState: false is explicitly set and eventSections is already undefined (since lastExecutions is always empty in the builder).

• web_src/src/ui/CustomComponentBuilderPage/storybooks/mockBlueprint.tsx: Removed hardcoded eventSections from storybook mock data so the storybook accurately represents how builder nodes appear without event/execution data.

How it works

The builder's createBlockData function already correctly:

1. Passes lastExecutions: [] to mappers, which return eventSections: undefined
2. Overrides includeEmptyState: false to prevent the empty state from showing

The only issue was merge nodes using a separate MergeComponent renderer that bypassed this override. This PR fixes that by rendering all builder nodes consistently through ComponentBase.

Closes #632

  

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