feat: implement MVP of gomongo library

[h3n4l]

Summary

Implement the initial version of gomongo - a Go library that parses MongoDB shell syntax and executes commands using the native Go MongoDB driver, eliminating the need for external mongosh CLI.

MVP scope (matching bytebase/bytebase#18883):

• db.collection.find() - returns all documents (filter parsed but ignored)
• Collection access via dot notation (db.users), bracket notation (db["user-logs"]), and getCollection()
• Extended JSON (Relaxed) output format
• Parse errors with line/column information
• Unsupported operation errors with hints

Not yet supported (future PRs):

• Filter support for find()
• findOne()
• Cursor modifiers (sort, limit, skip, projection)
• Helper functions (ObjectId, ISODate, UUID, etc.)
• Shell commands (show dbs, show collections)

Also includes:

• GitHub Actions workflows for tests and linting
• Integration tests using testcontainers
• ANTLR replace directive for Bytebase's optimized fork

Test plan

• go build ./... passes
• golangci-lint run passes with no issues
• go test -v ./... passes (integration tests with MongoDB testcontainer)

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR implements the MVP version of gomongo, a Go library that parses MongoDB shell syntax and executes commands using the native Go MongoDB driver. The implementation provides basic find() operation support with proper error handling and integration testing.

Changes:

• Implements core parsing and execution pipeline using ANTLR-based MongoDB parser
• Adds comprehensive integration tests with testcontainers for MongoDB
• Sets up GitHub Actions workflows for automated testing and linting

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
go.mod	Module definition with dependencies and ANTLR replace directive
go.sum	Dependency checksums
client.go	Public API with Client wrapper and Execute method
executor.go	Core execution pipeline: parsing, translation, and operation execution
translator.go	ANTLR visitor implementation for extracting operations from parse tree
errors.go	Custom error types for parse and unsupported operation errors
executor_test.go	Integration tests covering find operations and error scenarios
README.md	User documentation with usage examples and feature status
CLAUDE.md	Developer guidance for AI assistants
.github/workflows/tests.yml	GitHub Actions workflow for running tests
.github/workflows/lint.yml	GitHub Actions workflow for linting

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.