Changes the nested block syntax detection from requiring `@`
as the first non-space character on a line to using a line-ending brace heuristic.
The parser now recognizes nested blocks when a line ends with an unquoted `{`,
simplifying the syntax and removing the mandatory `@` prefix while maintaining the same functionality.
The default rule should runs only when no non-default pre rule matches, instead of running first as a baseline.
This follows the old behavior as before the pr is established.:
- Default rules act as fallback handlers that execute only when no matching non-default rule exists in the pre phase
- IfElseBlockCommand now returns early when a condition matches with a nil Do block, instead of falling through to else blocks
- Add nil check for auth handler to allow requests when no auth is configured
- Fix unterminated environment variable parsing to preserve input
Updates tests to verify the new fallback behavior where special rules suppress default rule execution.