feat(plugins): add OpenClaw target

[Elzlxx]

Summary

Adds an OpenClaw installer target so codegraph install (and the standalone installer) auto-wires the CodeGraph MCP server into OpenClaw. OpenClaw becomes the 9th supported agent — joining Claude, Cursor, Codex, opencode, Hermes, Gemini, Antigravity, and Kiro.

What's in this PR

• src/installer/targets/openclaw.ts (new) — implements AgentTarget for OpenClaw:
  • Detects ~/.openclaw/openclaw.json (falls back to $XDG_CONFIG_HOME/openclaw/)
  • Writes mcp.servers.codegraph with absolute codegraph binary path, --serve --mcp --path <project>, CODEGRAPH_TELEMETRY=0, and the project cwd
  • Single global location (OpenClaw is a single gateway, no per-project config layer) — supportsLocation('local') returns false and install('local') returns a note and writes nothing
  • Surgical mcp.servers.codegraph write — preserves all sibling MCP servers (chrome-mcp, wordpress-deltabis, user-defined) and all other top-level config keys (channels, agents, gateway)
  • Idempotent: byte-identical re-runs return action: 'unchanged'
  • Uninstall drops only mcp.servers.codegraph; siblings and other keys intact
  • Project root auto-detected by walking up from cwd looking for .codegraph/, mirroring codegraph init behavior
• src/installer/targets/registry.ts — registers openclawTarget
• src/installer/targets/types.ts — extends TargetId union with 'openclaw'
• __tests__/installer-targets.test.ts — 13 new openclaw-specific tests (sibling preservation, top-level config preservation, idempotency, uninstall, local-install refusal, detect transitions)
• README.md — adds OpenClaw to supported-agents badges and prose

Test Results

Suite	Result
installer-targets (157 tests)	all pass
Full suite (1549 tests, 80 files)	all pass
npm run build (tsc)	clean

The 13 new openclaw tests cover: greenfield install, sibling MCP preservation, sibling top-level config preservation (channels/agents/gateway), idempotent re-run, uninstall with siblings intact, local install refusal with note, and the before/after detect transitions.

Why OpenClaw

OpenClaw is an open-source multi-agent gateway (github.com/openclaw/openclaw) with a Claude/Codex-style config format. It's a natural fit — single global config dir, MCP server entries in a mcp.servers namespace, same write pattern as the existing 8 targets.

The contributor (Elzlxx) runs OpenClaw as a 4-agent production setup and will use this target daily for code exploration on geoxylia-audit, SkillOpt, and kobe-capital.

Notes

• Follows the same single-file-per-target + registry-entry + TargetId union pattern as the existing 8 targets. Mirrors the opencode test scaffolding (env-redirection via setHome(), XDG_CONFIG_HOME handling, etc.).
• Resolves the codegraph binary via common install locations (~/.local/bin/codegraph, ~/.codegraph/bin/codegraph, /usr/local/bin/codegraph, /opt/homebrew/bin/codegraph) with a PATH-resolved fallback.
• Reuses the existing jsonDeepEqual shared helper for idempotency detection.

License

MIT (consistent with the rest of the repo).