docs: improvement of architecture documentation

[Copilot]

This PR enhances the architecture documentation for Blaze, providing a comprehensive overview of package roles, build/runtime stages, and inter-package relationships.

Changes

• Architecture Overview: Added detailed explanation of Blaze's multi-package structure, clarifying build-time (compiler packages) vs runtime (reactive rendering) responsibilities
• Key Terms Section: Defined core concepts (Spacebars, Template, Template Instance, View) with their relationships and lifecycle phases
• Relationship Diagram: Fixed diagram to accurately represent Template Instance → View references and data flow between components

Note

This PR contains documentation-only changes. The CLA signature requirement mentioned in comments needs to be handled by the human contributor associated with this account, as AI agents cannot sign legal agreements.

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