examples: richer per-rule comment headers in sample policy.yaml

[CodewithJha]

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Context

examples/openai_support_agent/policy.yaml is the first policy people read. It already has one-line comments per rule. The scaffold template in mutiny init (POLICY_YAML in init_cmd.py) uses richer boxed headers (what it checks / what to edit). The sample should teach at that level.

Goal

Upgrade sample rule comments to clear per-rule headers (intent + operator/kind + edit hint) without changing YAML behavior.

Why it matters

Comments are the cheapest operator tutorial. Aligning sample ↔ scaffold reduces “which file is the real example?” confusion.

Acceptance criteria

• Each rule has a short header comment explaining intent / kind / what a newcomer might edit
• YAML remains valid; cd examples/openai_support_agent && uv run mutiny run --no-hosted still works (or dry-parse / existing sample path)
• No behavior or rule semantic changes (same ids, tools, thresholds)
• PR description links this issue

Suggested files

• examples/openai_support_agent/policy.yaml
• Optional reference: header style in packages/mutiny_cli/src/mutiny_cli/init_cmd.py (POLICY_YAML)

Out of scope

• Adding/removing rules, Core changes, rewriting examples/policies/demo_support.json

Hints

• Copy the boxed-comment style from the init stub, then tailor wording to the three sample rules (refund_limit, delete_requires_confirm, deny_send_email).
• Keep the top-of-file banner that explains Hosted vs examples/policies/ harness.

Difficulty

XS · examples / docs · comments only

Docs

• Catalog: GOOD_FIRST_ISSUES.md #28