feat: distinguish premise and policy in prompt construction

[rlippmann]

Summary

Strengthens the generic prompt-construction writing-assistant example by showing premise and policy as distinct authoritative state roles.

The example now uses premise for factual document context, such as:

• set premise draft is a board update summarizing quarterly results
• change premise to draft is an internal engineering handoff for a sev-1 incident

It keeps use concise_style as the policy contrast.

The observable behavior remains provider-free and deterministic: the host builds different system prompts based on authoritative state. Premise changes document-context guidance, while policy changes explicit writing constraints.

Why

Most existing examples visibly emphasize policy-style state such as use and prohibit.

This change gives prompt construction a clearer premise-based example:

authoritative fact -> host-derived prompt construction

That helps show Context Compiler state is not only allow/deny policy. Premise represents factual context that changes how host request construction is derived.

Example metadata

• Enforcement point: prompt construction / request construction
• Domain: writing assistant
• Technology/runtime: generic Python and TypeScript
• Example type: minimal example
• Does this use directive drafter? should normally be no: no
• Does this derive state from model output? must be no for primary examples: no

Checklist

• Repository scaffolding / governance change
• One primary enforcement point
• Explicit authoritative state
• No model-derived state mutation
• Adversarial stub or equivalent test
• Observable runtime behavior change
• Domain vocabulary is natural
• Framework is secondary to the enforcement point
• Docs updated
• Tests/smoke checks added where practical

Notes

Validation performed:

• uv run --no-sync pytest python/tests/test_prompt_construction_writing_assistant.py
• ./scripts/validate_python.sh
• cd typescript/examples/prompt_construction/writing_assistant && npm test
• cd typescript/examples/prompt_construction/writing_assistant && npm run typecheck
• cd typescript/examples/prompt_construction/writing_assistant && npm run build
• ./scripts/validate_typescript_fast.sh
• npx --yes markdownlint-cli2 python/examples/prompt_construction/writing_assistant/README.md typescript/examples/prompt_construction/writing_assistant/README.md python/examples/prompt_construction/README.md typescript/examples/prompt_construction/README.md

All validation passed.