docs(agents): reorder variable naming guideline and clarify conditional syntax in bash style guide

- Reorder local variable naming rule in AGENTS.md for better flow
- Add clarification note about escaping brackets when replacing `[ ]` with `[[ ]]`
- Emphasize that `[]` acts as a regex filter in conditional expressions

AGENTS.md

@@ -29,8 +29,8 @@ The following guideline is heavily based on the [Bash Style Guide | ysap.sh](htt
 
 **Variables:** Distinct between local and environment vars.
 
-- Use lowercase names for local variables (e.g., `buildx_output`).
 - Use `local` for all variables inside functions.
+- Use lowercase names for local variables (e.g., `buildx_output`).
 - Use uppercase names for environment variables (e.g. `BUILDX_PLATFORM`)
 
 **Functions:**
@@ -43,6 +43,7 @@ The following guideline is heavily based on the [Bash Style Guide | ysap.sh](htt
 
 - Always use `[[ ... ]]` for conditional testing, not `[ ... ]` or `test`.
 - Use `((...))` for arithmetic comparisons (e.g., `((a > b))`).
+- When you replace `[]` with `[[]]` make sure to escape the brakets. The `[]` is a regex filter.
 
 **Command Substitution:**