feat: manage MCP server configs across agents

[machado144]

What

New mcp artifact kind: define an MCP server once (mcps/<name>/mcp.yaml), loadout merges it into each agent's native MCP config through the normal plan → confirm → apply gate.

command: npx
args: ["-y", "@modelcontextprotocol/server-github"]
env:
  GITHUB_TOKEN: ${GITHUB_TOKEN}
scope: user   # or project

Agent	user scope	project scope
claude-code	~/.claude.json	<project>/.mcp.json
gemini-cli	~/.gemini/settings.json	<project>/.gemini/settings.json
cursor	~/.cursor/mcp.json	<project>/.cursor/mcp.json

• Secrets never enter the store: secret-looking env/header keys must use ${VAR} placeholders (passed through verbatim); literals are rejected at new/add, doctor, bundle import, and sync render.
• New engine surface: TargetFile.Root (agent-home / user-home / project), --project on sync/status/diff, root-qualified state keys (old state files load unchanged), path-escape fence on every target, root-aware snapshots.
• Bundles round-trip MCP artifacts through dir, tar.gz and flat YAML (kind-generic already — plus an import-time secret gate).
• Codex (TOML comment-preservation blocker) and Antigravity (unverified path) report n/a — parked in ROADMAP with rationale.

Spec: docs/specs/006-mcp-configs.md (+ plan, R9 amended to match the repo's new/add split).

Tests

• Unit: MCPSpec parse/secret-gate tables, per-adapter render (both scopes), engine root resolution + fence + root-qualified state, bundle round-trip ×3 formats + tampered-secret rejection.
• Integration (real binary, temp HOME): sync writes all three agents' configs; no-confirm-no-write invariant extended to user-home + project roots; project scope via --project (state stays in the data dir); hand-edit → drifted-local, foreign mcpServers entries survive re-sync; literal secret refused end-to-end.
• make ci + make test-integration green; internal/web/dist rebuilt (mcp glyph).

🤖 Generated with Claude Code

[github-actions]

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Current title: feat: manage MCP server configs across agents