Implements support for ${@:N} and ${@:N:L} syntax to slice argument arrays
in prompt templates, following bash conventions.
Syntax:
- ${@:N} - All arguments from Nth position onwards (1-indexed)
- ${@:N:L} - L arguments starting from Nth position
Features:
- Bash-style slicing familiar to shell users
- 1-indexed for consistency with $1, $2, etc.
- Processes before simple $@ to avoid conflicts
- No recursive substitution of patterns in arguments
- Comprehensive edge case handling
Examples:
- ${@:2} with ["a", "b", "c"] -> "b c"
- ${@:2:1} with ["a", "b", "c"] -> "b"
- ${@:99} with ["a", "b"] -> "" (empty, out of range)
Test coverage: 24 new tests, all passing (73 total)
Closes#769
f869cc4ae5