Code review: PR #2593 — Fix DrawIO CLI docs, refactor context menu, correct XML generation

Review by @sraphaz (as requested by @davydkov).

Summary

This PR applies three sets of changes: CLI documentation fix, DrawIO context menu refactor, and XML generation adjustments. The direction is correct; there is one issue that will break the playground typecheck and a few minor suggestions.

What looks good

1. CLI docs (cli.mdx)

• --output, -o → --outdir, -o is correct and matches the handler in packages/likec4/src/cli/export/drawio/handler.ts.

2. Context menu refactor

• Extracting logic into useDrawioActions and the presentational DrawioContextMenuView reduces duplication and keeps the components easier to maintain.
• Using triggerImport in the DRAWIO_IMPORT_EVENT / DRAWIO_EXPORT_EVENT listeners in the Provider is consistent.
• DrawioContextMenuView with explicit props (opened, onClose, menuPosition, onImport, onExport, canExport) keeps the UI testable and reusable.

3. XML (generate-drawio.ts)

• Placing mxUserObject after <mxGeometry /> inside each vertex mxCell is correct and aligns with what draw.io expects.
• Using flattenMarkdownOrString and isEmptyish for description/technology improves typing and roundtrip behavior.

Issue that breaks typecheck

openMenu in the context menu is typed only with React.MouseEvent.

In DrawioContextMenuProvider.tsx (and in the DrawioContextMenuApi type):

openMenu: (event: React.MouseEvent) => void

But LikeC4Diagram expects (in packages/diagram/src/LikeC4Diagram.props.ts):

export type OnCanvasContextMenu = (event: ReactMouseEvent | MouseEvent) => void

So the callback may receive either React.MouseEvent or DOM MouseEvent. The code that calls onCanvasContextMenu (e.g. ReactFlow) can pass the native event.

Effect: when passing openMenu to onCanvasContextMenu in $viewId.tsx, the playground typecheck fails with:

error TS2322: Type '(event: MouseEvent<Element, MouseEvent>) => void' is not assignable to type 'OnCanvasContextMenu'.
  Types of parameters 'event' and 'event' are incompatible.
  Type 'MouseEvent | React.MouseEvent<...>' is not assignable to type 'MouseEvent<Element, MouseEvent>'.

Suggested fix: accept the union in the type and in the handler:

• In DrawioContextMenuProvider.tsx: in DrawioContextMenuApi, use
  openMenu: (event: React.MouseEvent | MouseEvent) => void
• In the hook that implements openMenu (in useDrawioActions or wherever openMenu is defined): use the signature
  (event: React.MouseEvent | MouseEvent) => void
  and keep using event.preventDefault(), event.clientX, event.clientY (they exist on both types).
• In DrawioContextMenu.tsx, in the render prop children, type the argument the same way:
  (onCanvasContextMenu: (event: React.MouseEvent | MouseEvent) => void) => React.ReactNode

That makes the handler compatible with OnCanvasContextMenu and the playground typecheck will pass.

Minor suggestions

1. Changeset
   The bot already noted there is no changeset. Since this PR touches docs, playground, and generators, adding a changeset (e.g. patch for @likec4/docs-astro, @likec4/playground, @likec4/generators) makes sense if you intend to version these changes.

2. handleImportFile typing
   In useDrawioActions.ts, handleImportFile is typed as (e: React.ChangeEvent). For clarity and alignment with <input type="file">, consider:
   (e: React.ChangeEvent<HTMLInputElement>).

3. Naming
   Current names (useDrawioActions, DrawioContextMenuView) are clear. An alternative used elsewhere is useDrawioContextMenuActions + DrawioContextMenuDropdown; either is fine as long as the rest of the drawio code is consistent.

Post-fix checklist

• Update openMenu type to (event: React.MouseEvent | MouseEvent) => void (API + hook + render prop).
• Run pnpm turbo run typecheck --filter='@likec4/playground' and ensure it passes.
• (Optional) Add a changeset; (optional) type handleImportFile as React.ChangeEvent<HTMLInputElement>.

After that, this PR looks ready to merge from my side (assuming tests and the rest of typecheck are already green).