feat!: migrate SuperDeck models to Ack 1.2

[leoafarias]

Summary

• migrate SuperDeck's runtime, demo, and Wizard models from dart_mappable/Ack typed-map wrappers to Ack 1.2 class-first models, generated schema facades, and explicit unknown-property policies
• preserve wire-schema boundary values, deep collection immutability, equality/hash behavior, and explicit-null clearing in copyWith
• align the coordinated 1.0 package APIs, generated contracts, docs, CLI entrypoint, and demo artifacts
• move deck planning to gemini-3.7-flash and composition/repair/Wizard turns to gemini-3.5-flash-lite through the current Google AI transport at each model's lowest thinking level
• harden generation by rejecting element/composition contradictions and normalizing overlong generated title headings from the approved plan
• refresh macOS CocoaPods locks for Flutter 3.44's Swift Package Manager integration

Validation

• fvm dart run melos run fix --no-select
• fvm dart run melos run build_runner:build --no-select
• fvm dart run melos run analyze --no-select
• fvm dart run melos run analyze:all --no-select
• fvm dart run melos run custom_lint_analyze --no-select
• fvm dart run melos run contracts:check --no-select
• fvm dart run melos run test --no-select
• fvm dart run melos run test:integration:macos --no-select (39 tests)
• npx --yes @docs.page/cli check
• release web build and Playground macOS debug build
• Playwright Chromium/WebKit smoke matrix; one transient Chromium semantics poll timeout passed on isolated rerun
• opt-in live superdeck_demo_10 generation smoke: 10/10 slides, 4 model requests, 3 generated images, 19.338s combined generation time, visual quality report passed

Review notes

• Ack 1.2.0 is published for ack, ack_annotations, ack_generator, and ack_json_schema_builder.
• An adversarial change review classified the final diff as KEEP (high confidence) after restoring a weakened flex-validation assertion to check ACK's nested #/flex / number_positive error contract.
• The migration intentionally removes the old mapper APIs in favor of fromJson/toJson and generated *Schema facades as part of the coordinated 1.0 release.

[github-actions]

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