Phase 0: scheduleragent + mcp-server read-only agent framework

Complete the natural-language scheduler agent's Phase 0 read-only pipeline:

Task #2 (API Key auth mechanism):
- New store/apikey.go: APIKey store (hash, validate, expiry)
- controllers/apikey.go: GenerateAPIKey finally persists + registers RBAC role
- controllers/auth.go: GetUsernameFromToken recognizes xce_ak_ prefix
- middleware/validatehandler.go: isValidToken handles API Key
- config/rbac.yaml: mcp_readonly role (view-only permissions)
- 6 new test files covering unit + integration full-chain

Task #3 (schedulerclient Go library):
- types.go: URM types (URMJob/URMQueue/URMNode/JobStatus/Metrics)
- client.go: read-only Client interface (6 methods)
- httpclient.go: resty-based HTTP implementation
- statusmap.go + _test.go: TDD status mapping (33 tests)

Task #4 (mcp-server binary):
- cmd/main.go: entry, reads XCE_API_URL/XCE_API_KEY, registers 6 MCP tools
- internal/app.go: tool handlers wiring schedulerclient to MCP stdio
- Uses github.com/mark3labs/mcp-go@v0.57.0 for stdio transport

All: go vet clean, go build clean, schedulerclient 33/33 tests pass.
mcp-server binary ~11MB arm64, CGO_ENABLED=0.

Architecture:
  Claude Code --stdio--> mcp-server --HTTP--> apiserver REST API --cgo--> C backend

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

src/frontend/mcp-server/cmd/main.go

@@ -0,0 +1,86 @@
+package main
+
+import (
+	"log"
+	"os"
+
+	mcps "github.com/mark3labs/mcp-go/server"
+	"github.com/mark3labs/mcp-go/mcp"
+
+	"mcp-server/internal"
+)
+
+func main() {
+	baseURL := os.Getenv("XCE_API_URL")
+	token := os.Getenv("XCE_API_KEY")
+
+	if baseURL == "" {
+		baseURL = "https://localhost:8080"
+		log.Printf("XCE_API_URL not set, defaulting to %s", baseURL)
+	}
+	if token == "" {
+		log.Fatal("XCE_API_KEY environment variable is required")
+	}
+
+	app, err := internal.NewApp(baseURL, token)
+	if err != nil {
+		log.Fatalf("failed to initialize: %v", err)
+	}
+
+	s := mcps.NewMCPServer(
+		"scheduler-agent",
+		"0.1.0",
+		mcps.WithResourceCapabilities(true, true),
+		mcps.WithLogging(),
+	)
+
+	// ── scheduler_list_jobs ──
+	s.AddTool(mcp.NewTool("scheduler_list_jobs",
+		mcp.WithDescription("List jobs in the cluster. Supports filtering by queue, owner, status, and pagination."),
+		mcp.WithString("queue", mcp.Description("Filter by queue name")),
+		mcp.WithString("owner", mcp.Description("Filter by job owner username")),
+		mcp.WithString("status", mcp.Description("Filter by status: pending|running|succeeded|failed|cancelled|suspended|unknown")),
+		mcp.WithNumber("limit", mcp.Description("Max results to return")),
+		mcp.WithString("page_token", mcp.Description("Pagination token from a prior response")),
+	), app.HandleListJobs)
+
+	// ── scheduler_get_job ──
+	s.AddTool(mcp.NewTool("scheduler_get_job",
+		mcp.WithDescription("Get detailed information about a specific job by its ID."),
+		mcp.WithString("id",
+			mcp.Description("Job ID"),
+			mcp.Required(),
+		),
+	), app.HandleGetJob)
+
+	// ── scheduler_list_queues ──
+	s.AddTool(mcp.NewTool("scheduler_list_queues",
+		mcp.WithDescription("List all queues/partitions and their current state (active, inactive, draining)."),
+	), app.HandleListQueues)
+
+	// ── scheduler_list_nodes ──
+	s.AddTool(mcp.NewTool("scheduler_list_nodes",
+		mcp.WithDescription("List all compute nodes with their resource usage and status."),
+	), app.HandleListNodes)
+
+	// ── scheduler_job_logs ──
+	s.AddTool(mcp.NewTool("scheduler_job_logs",
+		mcp.WithDescription("Retrieve the output logs of a job."),
+		mcp.WithString("id",
+			mcp.Description("Job ID"),
+			mcp.Required(),
+		),
+		mcp.WithNumber("tail", mcp.Description("Number of lines from the end to return (0 = all)")),
+		mcp.WithNumber("offset_bytes", mcp.Description("Byte offset to start reading from")),
+	), app.HandleJobLogs)
+
+	// ── scheduler_cluster_metrics ──
+	s.AddTool(mcp.NewTool("scheduler_cluster_metrics",
+		mcp.WithDescription("Get a snapshot of overall cluster resource usage and utilization."),
+	), app.HandleClusterMetrics)
+
+	log.Printf("Starting scheduler-agent MCP server (base-url: %s)", baseURL)
+	if err := mcps.ServeStdio(s); err != nil {
+		log.Fatalf("server error: %v", err)
+	}
+}