feat(cel-proto-parser): add CEL proto parser and deparser package

[pyramation]

feat(cel-proto-parser): add CEL proto parser and deparser package

Summary

Adds a new cel-proto-parser package to the dev-utils monorepo for working with CEL (Common Expression Language) Abstract Syntax Trees. The package provides:

• Deparser: Converts CEL AST back to expression strings (e.g., {callExpr: {function: '_>_', args: [...]}} → "x > 5")
• Proto Parser: Parses CEL protobuf definitions to generate TypeScript types, enums, and AST helpers
• AST Helpers: Factory functions for constructing CEL AST nodes
• AST Converter: Converts @marcbachmann/cel-js AST format to CEL proto format for round-trip testing
• Test Utilities: CelTest class and helper functions for fixture-based round-trip testing (similar to pgsql-parser's TestUtils and constructive-db's PrettyTest)
• CEL Fixtures: 100+ CEL expression examples across multiple fixture files

The deparser supports all CEL expression types including constants, identifiers, field access, operators, ternary conditionals, lists, maps, message construction, and comprehensions.

Updates Since Last Revision

Added comprehensive policy-shaped fixtures and fixed converter bugs:

• Added policy.txt with 34 OPA-ish Kubernetes admission control expressions
• Added rls-templates.txt with 17 RLS policy template expressions (direct_owner, membership, etc.)
• Fixed index access operator: converter now handles [] (was only handling index)
• Fixed unary negation: converter now handles !_ with single node args (not array)
• All round-trip tests now pass: basic.txt 16/16, policy.txt 34/34, rls-templates.txt 17/17

Run fixture tests with:

npx tsx scripts/test-roundtrip.ts __fixtures__/expressions/policy.txt

Known limitation: @marcbachmann/cel-js does not support bitwise AND (&) operator, so permission bitmask expressions cannot be round-trip tested.

Review & Testing Checklist for Human

• AST converter correctness: Review src/converter/index.ts - this translates between two different AST formats. Verify the operator mappings (especially the [] and !_ fixes) and special cases (like has() macro handling) are correct.
• ESM workaround for @marcbachmann/cel-js: The library is ESM-only but Jest runs in CommonJS. Jest tests use manually constructed ASTs instead of parsing real CEL strings. Run npx tsx scripts/test-roundtrip.ts __fixtures__/expressions/basic.txt to verify full round-trip parsing.
• Proto parser functionality is untested: The CelProtoParser class has no tests. Run pnpm generate to verify it works with the included syntax.proto fixture.
• Comprehension handling is incomplete: The deparseComprehension function falls back to outputting a comment for unrecognized patterns.

Recommended Test Plan

1. Run pnpm test in the package directory - 65 tests should pass (34 deparser + 31 converter/integration)
2. Run npx tsx scripts/test-roundtrip.ts __fixtures__/expressions/basic.txt (expect 16/16 pass)
3. Run npx tsx scripts/test-roundtrip.ts __fixtures__/expressions/policy.txt (expect 34/34 pass)
4. Run npx tsx scripts/test-roundtrip.ts __fixtures__/expressions/rls-templates.txt (expect 17/17 pass)
5. Run pnpm generate to test the proto parser with the CEL syntax.proto fixture

Notes

• The package structure mirrors pg-proto-parser from the pgsql-parser ecosystem as requested
• CEL syntax.proto is included from the official cel-spec repository
• The CelTest class follows patterns from constructive-db's PrettyTest and pgsql-parser's FixtureTestUtils
• Some utility functions in src/utils/index.ts appear unused but may be needed for future features

Requested by: Dan Lynch (@pyramation)
Devin session: https://app.devin.ai/sessions/0d3278ca3e0d43b5a267e42838295712

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