Provider isAvailable() was using executableExists() which only checks
filesystem paths, not PATH. Commands like ["claude", "--flag"] would
show as unavailable even though they'd launch fine. Switch to
isCommandAvailable() which uses findExecutable() for proper PATH
resolution. Un-export executableExists from the public API.
Fix Windows cmd.exe metacharacter escaping — &, |, ^, <, >, (, ), !
are now properly escaped with ^, and % is doubled. Add shared
escapeWindowsCmdValue helper used by both quoteWindowsCommand and
quoteWindowsArgument. Replace local quoteForCmd in spawn.ts.
Add server-tests-windows CI job to catch Windows-specific regressions.
Mohamed Boudra
95e112c185