docs: favor standard widgets in JaWS guidance

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The JaWS skill and widget guide previously presented a custom JawsUpdate override as the usual way to avoid duplicate initial attribute commands. That encouraged custom UI for attribute changes standard widgets can handle.

Use standard widgets with application getters for later changes and member methods returning template.HTMLAttr for initial markup. The checklist now requires a concrete behavior or measured cost before specialization, while documenting the JaWS Template wrapper exception. The guide removes the misleading custom input example and clarifies that getter commands are absent from initial HTML and HTMLInner resends content on updates.

Validation: checked the guidance against widget and Element implementations, verified the changed guide links, and ran git diff --check. Documentation only.