Document Run (on change) execution-only trigger behavior

## Summary

Document the updated **Run (on change)** behavior: it should queue only when
the workflow's execution-relevant state changes, rather than for
layout- and presentation-only edits.

## Rationale

This is a user-visible behavior change. Moving, resizing, recoloring,
renaming, collapsing nodes, changing group layout, or navigating the canvas
no longer starts a run. Users need clear documentation explaining why these
edits do not auto-queue and what kinds of workflow changes still do.

## Affected documentation

- `docs.comfy.org` documentation for Run (on change) / auto-queue behavior.
- If applicable, cross-reference workflow editing and execution guidance.

## Required changes

- Explain that Run (on change) reacts to execution-relevant workflow changes.
- List representative presentation-only changes that do not trigger a run:
node position, size, title, collapse state, groups, viewport/navigation,
and slot-label changes.
- Clarify that widget values, connections, executable node changes,
bypass/mute state, and relevant subgraph execution changes still trigger
auto-queueing.
- Note that built-in `Note` and `MarkdownNote` are presentation-only, while
third-party note-like nodes are conservatively treated as execution-relevant.

## Acceptance criteria

- Documentation accurately describes the trigger behavior and its user-facing
implications.
- Documentation provides enough examples for users to distinguish
presentation-only edits from execution-relevant edits.

## References

- Pull request: https://github.com/Comfy-Org/ComfyUI_frontend/pull/14041
- Review discussion: https://github.com/Comfy-Org/ComfyUI_frontend/pull/14041#discussion_r3681564892
- Requested by: @jaeone94