Slate transform namespaces should be hard-cut to editor methods

Problem

Slate v2 cannot claim editor.update(...) and editor methods as the primary runtime while Transforms.* remains exported, imported in fixtures, or used in runtime code.

Symptoms

• Transforms.* stayed green in contract tests after docs/examples were clean.
• Legacy transform fixtures imported Transforms from slate, keeping the old mental model alive.
• Removing the namespace mechanically exposed a real recursion bug: editor.insertText called itself when the old low-level Transforms.insertText path was replaced blindly.

What Didn't Work

• Keeping Transforms as thin sugar. That preserved a second-looking public write surface.
• Treating this as docs-only cleanup. The namespace survived in runtime imports, tests, and fixtures.
• A blind codemod from Transforms.foo(editor, ...) to editor.foo(...). Most calls were fine, but editor.insertText needed an internal low-level text insertion helper.

Solution

Hard-cut the public namespace and migrate callers:

• Stop exporting Transforms, GeneralTransforms, NodeTransforms, SelectionTransforms, and TextTransforms from the root slate surface.
• Use editor primitives such as editor.setNodes(...), editor.insertText(...), editor.select(...), and editor.applyOperations(...).
• Keep transform implementation modules internal only.
• Add a public-surface contract that fails if the root package re-exports the deleted namespaces.
• Preserve editor.insertText by routing its low-level text path through an internal applyInsertText(...) helper instead of recursively calling the semantic method.

Why This Works

The public runtime has one write story:

editor.update(() => {
  editor.setNodes({ type: 'heading-one' })
})

Operations and implementation helpers still exist, but users and tests do not reach for a second Transforms.* namespace. The insertText split matters because semantic text insertion owns marks and command dispatch, while the internal text helper owns exact text operations.

Prevention

• Keep a root-surface test asserting the deleted namespace names are absent.
• Grep for Transforms.* outside generated historical output before claiming closure.
• Do not replace low-level helper calls blindly inside semantic editor methods.
• Use editor.applyOperations(...) for raw operation replay and editor methods inside editor.update(...) for document writes.