feat: add rego-deparser package for OPA Rego AST to text conversion

[pyramation]

feat: add rego-deparser package for OPA Rego AST to text conversion

Summary

Adds a new rego-deparser package to the dev-utils monorepo, positioned alongside cel-proto-parser. This package provides TypeScript types for OPA's Rego Abstract Syntax Tree and a deparser that converts AST back to valid Rego source code.

The package supports:

• All major Rego constructs: packages, imports, rules (complete, partial, default), else clauses
• Expressions with infix operators (comparison, arithmetic, assignment, unification)
• Data structures: arrays, sets, objects, references
• Comprehensions: array, set, and object comprehensions
• With modifiers and negation

This is part of the broader effort to add OPA capabilities to the stack for a unified policy engine.

Review & Testing Checklist for Human

• Verify AST types match actual OPA output: The types in src/types.ts were created from OPA documentation research. Test with real OPA-generated AST JSON (via opa parse --format json) to confirm the types are accurate
• Check infix operator mappings: The InfixOperators map in src/types.ts assumes specific operator names from OPA (e.g., assign → :=, eq → =). Verify these match OPA's actual AST representation
• Review for missing Rego constructs: Some features may not be covered (e.g., some keyword declarations, raw strings, certain every expression patterns)
• Consider adding to CI test matrix: The package has 47 passing tests but is not yet in .github/workflows/ci.yml

Suggested test plan:

1. Install OPA CLI locally
2. Create a sample Rego policy with various constructs
3. Run opa parse --format json policy.rego to get AST
4. Use the deparser to convert back to Rego
5. Compare output with original (or run through opa fmt for canonical comparison)

Notes

• Lint command fails due to existing ESLint 9 config format issue in the repo (not introduced by this PR)
• Build and all 47 tests pass locally

Link to Devin run: https://app.devin.ai/sessions/c053d7e3447a47959bc24118acd8b30c
Requested by: Dan Lynch (@pyramation)

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