add-providerlisted

# Add Provider Procedure We follow a strict Spec-Driven Development (SDD) workflow. When requested to add a new MCP provider to `usync`, strictly follow these steps: ## 0. SDD Pre-requisite Ensure an approved specification document exists (e.g., `docs/specs/add-<name>-provider.md`). If it doesn't exist or hasn't been approved, use the `agentic-sdd-router` or `agentic-sdd-spec` skill to create and refine the spec first. Do not proceed to implementation without a spec. ## 1. STOP and gather Read the following files to understand the system context: - `pkg/provider/types.go` - `pkg/provider/exa.go` - `pkg/provider/context7.go` - `docs/contributors/adding-a-provider.md` - `docs/specs/providers/add-context7-provider.md` ## 2. Look up official docs Use your search tools (or the Context7 MCP if available) to query the target server's configuration schema. Identify if it requires an API key, env vars, or specific arguments. ## 3. Decide capabilities Use the decision tree from `adding-a-provider.md`: - Is it `stdio` or a remote transport? - Does it use URL query auth or Header auth? - Is it a single-key or multi-key setup? ## 4. Scaffold helpers If necessary, create a package at `pkg/<id>/` for validation logic (e.g., `keys.go`, `keys_test.go`). Reference: `references/code-templates.md` (Template 1). ## 5. Implement provider Create `pkg/provider/<id>.go` implementing the `MCPProvider` interface. Reference: `references/code-templates.md` (Template 2). ## 6. Register Register yo