Enhanced Shell Security Checks

New Zsh-specific and general shell security checks for the Bash tool:

• Zsh process substitution =() — detected and flagged
• Zsh glob qualifiers with command execution (+ — detected and flagged
• Zsh try/always constructs } always { — detected and flagged
• Dangerous Zsh builtins (zmodload, zpty, ztcp, zsocket, zf_rm, etc.) — blocked
• fc -e command detection — prevents arbitrary command execution via editor
• Backslash-escaped operators — detects \;, \|, \&, \<, \> outside quotes that can hide command structure
• Comment quote desync — detects quote characters inside # comments that can confuse quote tracking
• Tilde expansion variants (~user, ~+, ~-) — require manual approval
• Compound cd + git commands — flagged to prevent bare repository attacks