refactor: component loading mechanism rewrite (V2)

[davidfirst]

Summary

RFC and implementation for rewriting the component loading mechanism. The current WorkspaceComponentLoader is ~1,000 lines of complex code that's hard to understand, modify, and debug.

Key Problems Being Addressed

• Complex caching with inconsistent keys (12 options, only 4 used in cache key)
• Recursive loading that's hard to trace (component → env → env-of-env → extensions)
• Legacy hooks that jump between code and Harmony unpredictably
• Multiple overlapping caches with no unified invalidation

Approach: Strangler Fig Pattern

• Build V2 loader alongside existing code
• Migrate command-by-command with parallel execution for comparison
• Remove V1 only after all e2e tests pass

See docs/rfcs/component-loading-rewrite/ for full RFC, task tracking, and architecture decisions.