Addressed multiple security vulnerabilities, crash scenarios, and resource management issues identified through comprehensive code analysis.

Security Fixes

• Command injection in PTY operations: Shell environment variables were concatenated without escaping. Now properly escaped per shell type (bash/zsh use '"'"', PowerShell doubles quotes, CMD escapes special chars with ^)
• PATH corruption: Duplicate pathDir entries caused incorrect binary resolution. Removed redundant append
• Error silencing: Version constraint matching errors were ignored with _, masking failures. Now propagated with context

Stability Fixes

• Panic on startup: os.UserHomeDir() failure caused panic. Now falls back to temp directory
• Array bounds panic: cache.go accessed n[1] without length validation. Added bounds check and skip malformed entries
• Infinite loop: Parent process traversal had no exit condition. Added 100-iteration limit and PID 1 check
• Filename corruption: Trailing space in Linux ARM64 target broke file paths

Resource Management

• Defer ordering: Environment variables restored before being set. Moved defer after assignment
• Goroutine leak: Reader goroutine cleanup had race condition. Separated stop/done channels for proper synchronization
• File cleanup timing: Downloaded archives deleted before extraction errors could be investigated. Now removed only on success
• ContentLength handling: Progress bar creation didn't handle -1 (unknown size). Added validation

Code Quality

• Standardized error wrapping using pkg/errors for stack traces
• Added error checking for critical write operations
• Removed redundant permission logic (already set on file creation)

Example of escaping fix:

// Before - vulnerable to injection
ptmx.Write([]byte(fmt.Sprintf("export %s='%s'", k, v)))

// After - shell-specific escaping
escapedValue := strings.Replace(v, "'", "'\"'\"'", -1)
ptmx.Write([]byte(fmt.Sprintf("export %s='%s'", k, escapedValue)))

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