refactor(workbench): share safe source path validation

[mldangelo-oai]

Summary

Use one implementation for validating finding source paths.

Changes

• Import the existing source-excerpt path validator into the workbench database module.
• Delete the identical duplicate implementation while preserving both modules' existing helper names.

Testing

• bun test tests-ts/plugin-report-limits.test.ts tests-ts/scan-recovery.test.ts --timeout 30000 — passed.
• python3 -I -B import and path-boundary smoke test — confirmed both modules share the same helper, safe paths remain accepted, and traversal/backslash paths remain rejected.
• pnpm run types — passed.
• git diff --check — passed.

Risk and rollout

The shared helper is byte-for-byte equivalent to the removed implementation. Existing repository containment, path traversal, and source-excerpt protections remain unchanged.

Public disclosure review

• No customer, partner, prospect, or user identities, data, or identifying details are included.
• No credentials, personal data, private source, scan findings, or nonpublic links or tickets are included.
• I reviewed the branch name, title, description, commits, changes, comments, logs, screenshots, attachments, and links for public disclosure.

[mldangelo-oai]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Keep them coming!

Reviewed commit: 42cbd91277

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[chatgpt-codex-connector]

Security review completed. No security issues were found in this pull request.

Reviewed commit: 42cbd91277

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[zcrab-oai]

Looks good. Reuses the identical safe source-path validator without weakening traversal, symlink, or Windows path protections.