docs: fix permission system documentation in agents section
What does this PR do?
Updates the agents section in the permissions documentation to reflect the new granular rules system. The previous examples showed mismatched patterns (e.g., "git status" without wildcards) that didn't properly demonstrate how pattern matching works for commands with arguments. The fix adds "grep *" examples to clearly demonstrate when pattern matching is essential, updates the explanatory tip to show both scenarios (commands that work without arguments vs. commands that require pattern matching).
How did you verify your code works?
Ran the docs development server locally to verify the changes render correctly and the examples are properly formatted. The documentation now accurately reflects how the granular permission system works with clear examples showing when to use pattern matching for commands that accept arguments like grep, versus commands that work with basic usage like git status.