ML-175: parse bash commands structurally via unbash
Replace regex-based command blocking with structural AST parsing
using unbash (zero-dependency TypeScript bash parser). The walker
collects command names only from executable positions (simple
commands, pipelines, subshells, command substitutions, control-flow
bodies), excluding arguments, comments, and quoted strings.
- Convert to directory-style extension with pinned unbash@3.0.0
- Add AST walker (ast.ts) covering 15 shell construct types
- Update blocked_commands to plain names instead of regexes
- Keep regex fallback for parse failures (degradation path)
- Path-based blocking unchanged for non-bash tools
- 41 tests cover blocked/allowed cases including false positives
Claudio Ortolina
a88c704fe5