docs: fix permission rule ordering in examples

[kdcokenny]

Problem

Permission examples show catch-all "*" rules at the bottom, but OpenCode uses "last matching rule wins" — so the catch-all overrides all specific rules above it.

Solution

Move "*" rules to the top of permission blocks so specific rules can override them.

Changes

• agents.mdx: Fix YAML and JSON examples, clarify explanatory text
• skills.mdx: Fix JSON example