Add 7 missing SDK methods and fix README type name

- Fix AgentKeyRequest → RegisterAgentKeyInput in README
- Add ListAgents, UnfreezeAgent, DeleteAgent to agents.go
- Add GetMe, IssueApiToken to auth.go
- Add DownloadExport to exports.go
- Add Health package-level function in health.go
- Add corresponding types and document all exports in README

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

auth.go

@@ -122,3 +122,21 @@ func authPost(baseURL, path string, body interface{}, result interface{}) error
 		Message:    string(respBody),
 	}
 }
+
+// GetMe retrieves the current authenticated user's profile.
+func (c *Client) GetMe() (*GetMeResponse, error) {
+	var result GetMeResponse
+	if err := c.doGet("/v1/auth/me", &result); err != nil {
+		return nil, err
+	}
+	return &result, nil
+}
+
+// IssueApiToken creates a new API token with an optional TTL.
+func (c *Client) IssueApiToken(req *IssueApiTokenRequest) (*IssueApiTokenResponse, error) {
+	var result IssueApiTokenResponse
+	if err := c.doPost("/v1/auth/token", req, &result); err != nil {
+		return nil, err
+	}
+	return &result, nil
+}