What

Three new API reference pages — docs/api/events.md, docs/api/mutations.md, docs/api/platform_metrics.md — plus nav entries, index rows, and the removal of two now-duplicate render blocks from docs/api/native_views.md.

Closes #24.

Why

The issue describes all three modules as having "no page at all." That's true only for platform_metrics. events and mutations were already fully rendered as sections of native_views.md (:32 and :23). Adding new pages without removing those blocks isn't a cosmetic duplication — it breaks CI: constructed in a scratch copy, it produces Aborted with 49 warnings in strict mode!, one mkdocs_autorefs: Multiple primary URLs found per symbol across all 13 public names in events, because two anchors leave autorefs unable to resolve any of the 21 site-wide references to them.

So the pure-addition task in the issue is really a small restructuring, which is what @owenthcarey confirmed.

How (brief)

• Three new pages following docs/api/reconciler.md: title, one-paragraph summary, the
  mkdocstrings block with identical options and filters, then Next steps.
• The ::: blocks for mutations and events are removed from native_views.md, leaving a
  one-line pointer under each existing heading, per @owenthcarey's direction on the issue.
• Nav entries sit directly after Native views rather than appended, keeping them adjacent to
  the page that points at them and inside the internals cluster.
• Per the second ask, all four pages cross-link: each new page's Next steps names the other two
  plus Native views, and Native views names all three.
• IOS_TAB_BAR_BASE_HEIGHT_PT is a documented public constant that mkdocstrings silently
  dropped, because platform_metrics.py was the only file in src/pythonnative/ documenting an
  attribute with Sphinx-style #: comments, which griffe doesn't parse as a docstring.
  Converting four comment lines to a PEP 258 docstring, matching events.py:27, is a runtime
  no-op — value and type verified unchanged — and makes the constant render. The alternative,
  show_if_no_docstring: true on the page, would have surfaced every other undocumented
  attribute as a side effect.

Testing

• site/ deleted and rebuilt from clean, mkdocs build --strict exit 0.
• ./scripts/check.sh passes end to end.
• Each page verified against its module's AST to render exactly the expected symbols with no typing leakage, and the HTML grepped for duplicate anchors: 34 symbols, each with exactly one, and zero left on native_views.
• Cross-reference audit (Owen's ask): all 25 references were traced through the generated HTML one by one. None needed editing — every reference names a symbol rather than a page, so autorefs re-pointed all 21 that render, and the remaining 4 live in the deliberately unrendered platform handler modules. One reference improved for free: platform_metrics.py:153 pointed at set_safe_area_insets, which previously resolved to nothing.

Risks/Impact

Anchors for the events and mutations symbols move from api/native_views/ to the new pages.
Every in-repo reference re-points automatically, but an external bookmark or link to something
like api/native_views/#pythonnative.events.dispatch_event will still reach a valid page and
no longer reach that anchor. Unavoidable given the move, and the reason for keeping the two
pointer lines where the sections used to be.

Docs/Follow-ups

Two disclosed additions beyond the acceptance criteria, both deliberate:

• Rows in docs/api/pythonnative.md's "Where to look next" table for all three pages. The
  criteria don't mention it, but every other API page has a row, and a page absent from the
  index is a page readers won't find.
• The native_views.md intro now links "mutation ops" to the new page, since that prose
  promised content that has moved.