Update docs for Streamlit 1.63.0 release

[sfc-gh-mbarnes]

Summary

• Add 1.63.0 release notes to release-notes/_index.md (as latest) and prepend the 1.63.0 section to release-notes/2026.md, covering event-scoped fragment reruns, on_change="ignore", and type="step" containers.
• Generate docstrings for Streamlit 1.63.0 into python/streamlit.json (single new "1.63.0" top-level key appended; no existing version keys modified).
• Surface the two new AppTest members on the AppTest API page: AppTest.get_by_key (a keyed retrieval method, next to AppTest.get) and AppTest.container (a block-sequence property, next to AppTest.columns). That page declares each member explicitly, so newly generated keys do not appear without it.
• Skip AppTestError in generate.py. Streamlit 1.63.0 newly exports it from streamlit.testing.v1, and inspect.signature() raises on an exception class, which aborted generation.
• Document the new runner.cacheBackgroundRefreshTTLMultiplier config option in config-toml.md.
• Add three Community Cloud example apps for the new type="step" and select_all examples.

No new commands were introduced in 1.63.0 (only new parameters and modes on existing commands, such as st.rerun(scope=...), @st.fragment(key=...), on_change="ignore" on st.slider / st.text_input, type="step" on st.expander / st.status, wrap on more commands, icon on headings, and st.multiselect(select_all=...)), so no new API tiles, detail pages, menu entries, or illustration images were added. Nothing was removed or newly deprecated, so there are no deprecation stubs.

Test plan

• Verify the 1.63.0 section renders correctly on /develop/quick-reference/release-notes and /develop/quick-reference/release-notes/2026, and that the 1.62.0 section is unchanged in the 2026 archive.
• Spot-check Autofunction pages for the new parameters: st.rerun, st.fragment, st.slider, st.text_input, st.expander, st.status, st.multiselect, st.title, and AppTest.
• Confirm AppTest.get_by_key and AppTest.container render on the AppTest page, in the "Get AppTest script elements" section.
• Confirm runner.cacheBackgroundRefreshTTLMultiplier appears in the [runner] block on the config.toml page.
• Deploy the new example apps (table below), then confirm the Cloud embeds load on st.expander, st.status, and st.multiselect.

App	Deploy link	GitHub file	Subdomain
st.expander timeline steps (type="step")	Deploy	layout.expander_step.py	doc-expander-step
st.status timeline steps (type="step")	Deploy	status.status_step.py	doc-status-step
st.multiselect bulk-select control (select_all)	Deploy	widget.multiselect_select_all.py	doc-multiselect-select-all

🤖 Generated with Claude Code

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