Add Grok Build (xAI) support

[whaleen]

What

Add read-only observation support for Grok Build — xAI's agentic coding CLI (launched May 2026), analogous to what project-index already does for Claude Code, Codex, Gemini, and Pi.

Known storage locations

Artifact	Path
Config	~/.grok/config.toml
User settings	~/.grok/user-settings.json
Sandbox profile	~/.grok/sandbox.toml or .grok/sandbox.toml
Sessions / history	~/.grok/ (exact subdir TBD)
Generated media	~/.grok/generated-media/
Binaries	~/.grok/bin/grok and ~/.grok/bin/agent

Binary

grok — invoked as grok in the terminal, installed via curl -fsSL https://x.ai/cli/install.sh | bash

What to implement

• Sessions: discover and list Grok sessions from ~/.grok/ — format TBD, needs inspection of a live install
• Memory: read any persistent memory/context Grok stores (experimental memory commands exist, locations unclear)
• Config surface: observe ~/.grok/config.toml, ~/.grok/user-settings.json, .grok/sandbox.toml in the Context tab
• Agent docs: add docs/agents/grok.md documenting storage interface (same pattern as docs/agents/claude.md etc.)
• AgentKind: add AgentKind::Grok and MemoryAgent::Grok variants
• SPEC.md: update Sessions, Memory, and Context surface sections

Notes

• Grok Build is early beta as of May 2026 — storage format may change
• grok inspect shows discovered config, instructions, skills, plugins, hooks, and MCP servers — worth checking if this output is parseable
• Session storage format unknown until someone with a live install can check ~/.grok/ — may be JSONL like Claude/Pi or different
• The agent binary (alongside grok) may have its own storage pattern worth investigating

References

• https://x.ai/news/grok-build-cli
• https://docs.x.ai/build/overview
• https://x.ai/cli