feat: add OpenCode and Antigravity CLI providers

[AtharvaGurao]

Summary

Adds two new free CLI-based LLM providers as requested in #68.

New Providers

Provider	CLI Tool	Command
OpenCode	opencode-ai/opencode	opencode -p "prompt" -f json -q
Antigravity/Gemini CLI	google-gemini/gemini-cli	gemini -p "prompt" --sandbox false

Both are free and follow the same subprocess pattern as the existing ClaudeCliProvider.

Provider Names in Config

{"agents": {"defaults": {"provider": "opencode"}}}
// or
{"agents": {"defaults": {"provider": "antigravity"}}}

Aliases: open-code, gemini-cli

Files Changed

• pkg/providers/opencode_provider.go — new OpenCode CLI provider
• pkg/providers/antigravity_provider.go — new Antigravity/Gemini CLI provider
• pkg/providers/http_provider.go — wired into CreateProvider()
• pkg/config/config.go — added config entries
• .env.example — documentation

Testing

• ✅ All existing tests pass
• ✅ Build succeeds

Closes #68

[mengzhuo]

Could you rebase and do make fmt?

[vantuan88291]

When this can be merge?

[mengzhuo]

When this can be merge?

You need to make fmt and resolve confilcts.

[vantuan88291]

I think Antigravity and gemini not the same cuz when login via Antigravity i got more models than just provide gemini api key, and Antigravity provided oauth login, not api key

[AtharvaGurao]

Rebased onto latest main and ran make fmt. Conflicts resolved (merged in the new Ollama, DeepSeek, GitHubCopilot, and CodexCli providers from upstream). Ready for review!

[mrbeandev]

whats the status of this pr ? has anyone tested it ? is antigravity working ??

[Leeaandrob]

@Zepan Adds OpenCode and Antigravity CLI providers (+602 lines). These follow the same CLI subprocess pattern as the Codex CLI provider (#80, merged).

Recommendation: Review after #213 (Provider Refactor) lands. CLI providers are a good fit for PicoClaw's lightweight philosophy, but the provider architecture is about to change. These would need rework after #213.

[mrbeandev]

Sharing for visibility: we opened a follow-up implementation and validation PR here: #343

It includes Antigravity provider integration plus compatibility fixes found during testing (tool-call normalization, history ordering sanitization, thought_signature preservation).

[yinwm]

Thanks for the contribution! However, this PR needs significant rework due to architecture changes and overlapping implementations.

Current Status:

Feature	This PR	Main Branch
Antigravity	CLI-based (286 lines)	✅ Already exists - HTTP + OAuth (24,719 lines via #492)
OpenCode	CLI-based (282 lines)	❌ Not yet available

Issue 1: Antigravity Already Exists

PR #492 (Provider Refactoring) has been merged, which includes a complete Antigravity provider with:

• Full OAuth login flow
• HTTP-based API (not CLI subprocess)
• Better error handling and reliability
• See: pkg/providers/antigravity_provider.go

Issue 2: Architecture Changes

This PR modifies the old http_provider.go structure which has been replaced by the protocol-based model_list configuration. See: provider-refactoring.md

Suggested Path Forward:

1. Antigravity: Can be removed from this PR - already implemented
2. OpenCode: If you'd like to keep this, please rebase and:
   • Remove all Antigravity-related changes
   • Keep only pkg/providers/opencode_provider.go
   • Follow the pattern in pkg/providers/claude_cli_provider.go
   • Register in pkg/providers/factory_provider.go:

     case "opencode", "open-code":
         workspace := cfg.Workspace
         if workspace == "" {
             workspace = "."
         }
         return NewOpenCodeProvider(workspace), modelID, nil

Would you like to update this PR with only the OpenCode provider? Or I can close this and you can open a new focused PR.