Restore DynamicKeyboardBase as its own page in abstract-nodes/

[chrisdp]

Summary

Companion to #31 (LabelBase), #34 (Dialog), and #35 (LayoutGroup), addressing the fourth instance of the same consolidation pattern. Upstream commit 5435954e ("fixed superfluous index pages", May 6 2026) merged dynamic-voice-keyboard-nodes/dynamic-keyboard-base.md into the section index.md, deleting the dedicated DynamicKeyboardBase reference page and breaking 14 inbound doc:dynamic-keyboard-base link sites.

Like LabelBase, DynamicKeyboardBase is a genuine abstract base class — not directly instantiable; you only ever instantiate DynamicKeyboard, DynamicPinPad, DynamicMiniKeyboard, or DynamicCustomKeyboard, which all extend it. Its natural home is abstract-nodes/, matching the convention used by ArrayGrid, AnimationBase, and the just-merged LabelBase.

Why this restructuring matters

Same developer-impact concerns from the previous three PRs:

• Component clarity was lost. DynamicKeyboardBase is the abstract class all four dynamic-voice keyboard nodes extend. The docs are full of "Extends DynamicKeyboardBase" references that need a real page to land on. Folding the reference into the section index made DynamicKeyboardBase no longer searchable as its own node.
• The section landing stopped doing landing-page work. Post-consolidation it was a 103-line DynamicKeyboardBase reference dump with no overview of the four keyboard variants, no description of the underlying components (DynamicKeyGrid, VoiceTextEditBox, Key Definition File), and no signposting to legacy migration or the Standard dialog framework alternatives.
• Inbound doc:dynamic-keyboard-base links broke silently across 14 link sites.

What changed

• New page: docs/REFERENCES/scenegraph/abstract-nodes/dynamic-keyboard-base.md. Slug doc:dynamic-keyboard-base (preserved). Same content as the deleted page, with SEO metadata backfilled, fields-table HTML reformatted with proper indentation, and a typo fix ("dication" → "dictation" in two cells of the domain field description).
• Rewritten landing: docs/REFERENCES/scenegraph/dynamic-voice-keyboard-nodes/index.md. Short intro, certification blockquote, a representative DynamicKeyboard image, a Choosing-a-node table covering all four keyboard variants, a separate components table (DynamicKeyGrid / VoiceTextEditBox / Key Definition File), an Inheritance note, a Voice entry note (currently English and Spanish), a Looking-for-something-else section pointing at the legacy Keyboard / legacy PinPad and the Standard dialog framework's StandardKeyboardDialog and StandardPinPadDialog, and a sample-app pointer.
• Release notes file-path updates: 3 references in docs/DEVELOPER/release-notes/index.md (lines 461, 643, 655) rewritten from /docs/references/scenegraph/dynamic-voice-keyboard-nodes/dynamic-keyboard-base.md → /docs/references/scenegraph/abstract-nodes/dynamic-keyboard-base.md. Anchors preserved.

Inbound-link audit

Audited four ways: slug refs, file-path refs, camelCase variants, anchor refs into the old index. Findings:

• 14 doc:dynamic-keyboard-base slug references — resolve naturally to the new abstract-nodes location (slug unchanged): release-notes:1072 (no, sorry — that was for Dialog); the references include certification.md:207, cert-tests/index.md:546, the four sibling keyboard pages (dynamic-keyboard.md, dynamic-pinpad.md, dynamic-mini-keyboard.md, dynamic-key-grid.md, dynamic-custom-keyboard.md via <Anchor>), FEATURES/engagement/voice.md:36, VIDEOS/demos/summit-2021.md:17, and several in the rewritten landing itself.
• 3 file-path refs in release-notes — rewritten in this PR.
• 1 doc:dynamic-voice-keyboard-nodes reference (release-notes:593) — resolves to the rewritten section landing.
• camelCase/no-dash slug variants (doc:DynamicKeyboardBase, etc.) — 0.
• Anchor refs into the consolidated index — 0.