v2: overflow → auto-insert page

[gorlix]

Context

v1 ignores overflow: when content is pushed down past the page bottom it is clipped (off-page). For the v2 auto-move this becomes a real correctness concern.

Goal

When shifting content down would push it beyond the page height, automatically insert a new page and move the overflowing content there.

Approach

• After computing the shift, detect elements whose new y exceeds pageH.
• PluginFileAPI.insertNotePage({notePath, page, template}) to add a page.
• Move the overflowing elements onto the new page (insert there / delete from current), respecting the page-anchored insertion caveats (SKILL.md gotchas v1: landscape / rotation support #20, v1: component smoke test for App.tsx #22).
• Depends on chore(deps): Bump react-test-renderer from 19.0.0 to 19.2.7 #7 (auto-move) being in place.

Acceptance criteria

• Content beyond the bottom flows onto a newly inserted page.
• No data loss; page indices stay consistent.

References

• references/api-quick-ref.md (insertNotePage), SKILL.md gotchas v1: landscape / rotation support #20/v1: component smoke test for App.tsx #22/v2: overflow → auto-insert page #24
• Depends on chore(deps): Bump react-test-renderer from 19.0.0 to 19.2.7 #7