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>

CLAUDE.md

@@ -49,6 +49,7 @@ For details on any topic below, read the corresponding steering file in `.kiro/s
 - `src/worker/` — See `src/worker/CLAUDE.md`
 - `src/scheduler/` — See `src/scheduler/CLAUDE.md`
 - `src/lib/` — See `src/lib/CLAUDE.md`
+- `src/frontend/schedulerclient/`, `src/frontend/mcp-server/` — Phase 0 已完成（2026-07-26）。`schedulerclient` 是独立 Go library 提供只读 Client interface + resty HTTP 实现（33 单测）。`mcp-server` 是 MCP stdio 二进制（`github.com/mark3labs/mcp-go@v0.57.0`），通过 `schedulerclient` 调用 `apiserver` REST API，暴露 6 个只读 MCP Tool。Pure Go, `CGO_ENABLED=0`。总体架构与分阶段计划见根目录 `CLAUDE.md`（"Unified Scheduler Agent Framework"）。
 
 # Agentic SDLC and Spec-Driven Development