feat(memory): add history plugin and remove input wrappers

[cpluss]

Summary

• add a new history plugin API: cria.history({ history }), designed for ergonomic history composition with .use(...)
• remove .input wrapper support and PromptBuilder.input(...) to simplify history ingestion paths
• keep inputLayout as the low-level escape hatch and normalize PromptLayout inputs inside the history plugin
• update docs to document history plugin usage and link it from top-level documentation
• update plugin/builder tests for the new history flow and removed input wrappers

Breaking changes

• removed cria.input(...)
• removed PromptBuilder.input(...)
• removed exported PromptInput type
• scope content no longer accepts provider-native input wrappers

Validation

• npm exec -- ultracite check
• npm run build
• npm test

[cpluss]

Superseded by #49 (same changes rebased on latest main, with rewritten commit history and no in commit messages).