* shell: allow spaces in arguments via quoting (#8157)
- updated argument splitting regex to handle quoted segments
- added robust quote stripping to remove matching quotes from flags
- added unit tests for regex splitting and flag parsing
* shell: use robust state machine parser for command line arguments
- replaced regex-based splitter with splitCommandLine state machine
- added escape character support in splitCommandLine and stripQuotes
- updated unit tests to include escaped quotes and single-quote literals
- addressed feedback regarding escaped quotes handling (#8157)
* shell: detect unbalanced quotes in stripQuotes
- modified stripQuotes to return the original string if quotes are unbalanced
- added test cases for unbalanced quotes in shell_liner_test.go
* shell: refactor shared parsing logic into parseShellInput helper
- unified splitting and unquoting logic into a single state machine
- splitCommandLine now returns unquoted tokens directly
- simplified processEachCmd by removing redundant unquoting loop
- improved maintainability by eliminating code duplication
* shell: detect trailing backslash in stripQuotes
- updated parseShellInput to include escaped state in unbalanced flag
- stripQuotes now returns original string if it ends with an unescaped backslash
- added test case for trailing backslash in shell_liner_test.go
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