Configurable tap marker overlay styles and duration #69

Summary

Add options to control the visual marker shown for coordinate taps.

Requested behavior

When a coordinate tap is displayed on the page, callers should be able to choose the marker style:

• current blue circle
• crosshair marker with coordinate text

For the crosshair style, show two coordinate pairs:

• viewport coordinates, in CSS viewport pixels
• page coordinates, including the current page scroll offset

Callers should also be able to specify how long the marker remains visible before fading out.

Candidate API shape

Extend coordinate interaction endpoints such as tap with an optional marker object:

{
  "x": 120,
  "y": 240,
  "marker": {
    "style": "circle" | "crosshair-coordinates",
    "durationMs": 1500
  }
}

The exact field names can change during design, but the behavior should stay cross-platform and keep iOS, macOS, and Android visually aligned.

Acceptance criteria

• tap can keep the current blue circle behavior by default.
• Callers can request a crosshair marker with viewport and page coordinate text.
• Callers can configure marker display duration before fade-out.
• Behavior and API shape are mirrored across iOS, macOS, and Android.
• Docs and MCP/CLI schemas describe the marker options.