Refactor: Establish Block Editor Angular Standards and Documentation

[rjvelazco]

Description

The Block Editor lacks a consistent coding standard and sufficient documentation. This makes the codebase harder to maintain, extend, and onboard into. The goal of this task is to define an Angular-idiomatic standard for Block Editor development and improve documentation so that future work on this field is predictable and easier to reason about.

This includes: establishing patterns for component structure, service usage, signals, reactive forms, and dependency injection; auditing existing code against those patterns; and adding TSDoc to public APIs and non-obvious logic.

Acceptance Criteria

• A Block Editor coding standard document is defined and team-approved
• All public services and components have TSDoc covering purpose, inputs, outputs, and usage
• Block Editor code follows Angular idioms: signals, reactive patterns, DI, and component encapsulation
• Deviations from the standard are either fixed or tracked as explicit follow-up debt
• The standard document is linked from the Block Editor module README

Priority

Medium

Additional Context

Related PR: #35257 (Refactor: Block Editor)