[Blueprints] Document AccessibilityAttributes resolution and adapter mapping in a2ui_core and a2ui_framework_adapter blueprints

Problem

The v1.0 protocol specification (specification/v1_0/docs/a2ui_protocol.md:L483-L515) and core conformance suite (conformance/core/accessibility.yaml) define AccessibilityAttributes (label, description, hidden, live) on ComponentCommon, along with rules for default semantic inference and explicit attribute overrides.

However, the module blueprints under blueprints/modules/ do not yet document these requirements:

blueprints/modules/a2ui_core.blueprint.md does not specify how NodeResolver / GenericBinder and PayloadValidator handle ComponentCommon.accessibility across built-in and custom component schemas, or how nodes expose resolved vs. explicit accessibility attributes.
blueprints/modules/a2ui_framework_adapter.blueprint.md does not have a section specifying how framework adapters (renderers/lit, renderers/react, renderers/angular, swift/swiftui, dart/a2ui_flutter) map label, description, hidden, and live onto host views/elements so custom components inherit accessibility behavior automatically.

Update blueprints/modules/a2ui_core.blueprint.md (and blueprints/features/node_resolution.blueprint.md) to specify AccessibilityAttributes validation, dynamic binding resolution on ComponentCommon, and default semantic inference.
Add an Accessibility section to blueprints/modules/a2ui_framework_adapter.blueprint.md documenting the adapter-level mapping contract for label, description, hidden, and live.