feat: rebase fork capabilities onto upstream main

[aryasaatvik]

Summary

Rebase the fork's execution, history, Cloudflare, service-token, and semantic-search work onto current upstream.

Flow

request
  -> actor and trigger attribution
  -> composed execution observer
  -> history and metrics plugins
  -> Cloudflare Agent MCP session

Included

Surface	Outcome
Execution	Observer, metrics, actor attribution, history UI
Cloudflare	Current Agent MCP host plus service-token aliases
Search	AI Search backend, indexing pipeline, D1 FTS
Storage	Bulk operations, aggregation, keyset pagination

Validation

• bun run typecheck
• Candidate-only oxfmt --check
• Candidate-only oxlint --deny-warnings
• Focused execution, Cloudflare, OpenAPI, MCP, semantic-search, and cloud tests