perf(agent): streamline routine document generation

[iamjr15]

Why

Routine Word-document requests were still following the custom docx script workflow. In production that caused an unnecessary dependency probe, generated-script write, and a failed python invocation before retrying with python3.

What changed

• make docs_generate_docx the documented default for routine memos, reports, letters, briefs, and one-pagers
• reserve the custom docx/render workflow for template-driven, visually specialized, or explicitly inspected documents
• remove preflight install/probe instructions because the runtime is snapshot-bundled
• use python3 consistently in every executable DOCX skill example
• align the tool description with the authoritative one-call production path

Architecture and migration effects

No database, environment, deployment-topology, or public API changes. This only changes production agent guidance and tool metadata.

Verification

• pnpm lint
• pnpm typecheck
• pnpm turbo build --force
• pnpm deadcode
• pnpm architecture:check
• pnpm turbo skills:build

Production browser acceptance will be repeated after merge and Cloudflare deployment because the behavior is provided by the deployed agent worker.