Harden manifest validation and action input handling

[snapsynapse]

Summary

• Harden the composite GitHub Action against bundle-path shell injection.
• Make manifest hash validation fail closed, with explicit hash: null opt-outs and update-mode repair.
• Add CI regression scripts and expand coverage from 46 to 50 eval scenarios.
• Prepare the canonical bundle and release surfaces for version 5.0.0.

Root cause

The action interpolated caller-controlled input directly into Bash source. The validator also conflated missing or malformed hashes with intentionally unhashed entries, allowing an invalid manifest to report success.

Impact

Validation now rejects missing, malformed, and duplicate hash fields. Git-backed bundles must use explicit hash: null for intentional opt-outs. This is a breaking manifest-contract change and is therefore versioned as 5.0.0.

Validation

• Canonical bundle hash verification
• Validator hash-state regression suite
• Action input transport and adversarial-path regression
• Strict and ClawHub package builds
• Release-surface and .skill freshness checks
• Bash syntax and JSON validation
• Strict-platform skill validation

Follow-up

Path traversal, symlink handling, duplicate path entries, and the supported YAML-subset grammar remain policy questions. They are captured in a local ignored handoff and intentionally excluded from this PR.