feat(runner/llm-builtin): expose schema on result self-link and use in llm tools

[seefeldb]

also makes a bunch of parts that were async sync now, which might fix some races

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Summary by cubic

Expose the result schema on the process’s resultRef link and switch LLM tools to use it for schema discovery. This makes schema docs available in prompts and makes the schema tool faster and more reliable.

• New Features

  • Attach recipe.resultSchema to resultRef links (includeSchema) when available.
  • LLM dialog reads schema from cell.schema or resultRef.schema and appends brief schema docs to the system prompt.
  • The schema tool returns the discovered JSON Schema synchronously and works for any cell path.

• Refactors

  • Replaced async schema fetching with sync helpers; removed runtime recipe loading in LLM tools.
  • Made request startup synchronous to reduce race conditions.

^{Written for commit 5364e8d. Summary will update automatically on new commits.}