Adapt Bash parser to structural projections

[Aaronontheweb]

Summary

• replace the legacy flat Bash splitter with a recursive structural coordinator for lists, pipelines, subshells, and static shell wrappers
• require exact literal provenance before decoding bash/sh command strings; retain incomplete outer leaves for dynamic or noncanonical forms
• enforce structural depth limits before descent and add focused compatibility, span, identity, completeness, and hostile-depth coverage
• update SPEC, OpenSpec, and the implementation plan for the completed Bash structural slice

Security posture

Unknown executable regions, expanding wrapper bodies, unsupported wrapper tails, redirects, and undiscovered command substitutions remain incomplete or fail closed. Ordinary non-executable variable expansion does not unnecessarily invalidate the structural projection.

Validation

• Release build: 0 warnings, 0 errors
• Full test suite: 1,192/1,192
• Headers: pass
• dotnet format: pass
• OpenSpec strict validation: pass
• Slopwatch: 0 findings
• adversarial review: GO