[plan] Migrate from gh CLI shell-outs to native go-gh API clients

[github-actions]

Overview

This tracking issue covers the migration from shell-out gh.Exec() calls to native REST and GraphQL API clients provided by github.com/cli/go-gh/v2. This will improve performance (5-10x faster), simplify code, and follow upstream best practices.

Source: Discussion #5826 (Go Fan report on go-gh module usage)

Current State

The project uses gh.Exec() shell-outs for all GitHub API interactions across 4 files:

• pkg/workflow/repository_features_validation.go - Repository feature detection
• pkg/workflow/github_cli.go - Wrapper functions
• pkg/cli/exec.go - Conditional gh CLI usage
• pkg/parser/remote_fetch.go - Remote file downloads

Expected Benefits

• Performance: 5-10x faster (eliminates process spawning overhead)
• Code Quality: Type-safe API calls with automatic JSON handling
• Maintainability: Cleaner error handling and better testability
• Reliability: Built-in retry logic and caching support

Planned Tasks

This work is broken into focused, incremental tasks that can be completed independently:

1. #aw_a1b2c3d4e5f6 - Replace gh repo view with repository.Current()
2. #aw_b2c3d4e5f6a7 - Migrate repository features to REST client
3. #aw_c3d4e5f6a7b8 - Migrate GraphQL discussions check to native client
4. #aw_d4e5f6a7b8c9 - Migrate remote file downloads to REST client
5. #aw_e5f6a7b8c9d4 - Enable API caching and adopt pkg/auth

Success Criteria

• All gh.Exec() calls replaced with native API clients
• Performance benchmarks show 5-10x improvement
• All tests passing (unit + integration)
• Code simplified with better error handling
• API caching enabled for better performance

AI generated by Plan Command for discussion #5826