feat: implement orchestrator core (Rust)

Task 1.1: ✅ Cargo.toml with axum, rusqlite, matrix-sdk, serde, etc.
Task 1.2: ✅ Directory structure: src/core, src/adapters, src/integrations, src/api
Task 1.5: ✅ config.example.toml with full schema
Task 2.1: ✅ Data models: Agent, Task, Receipt, Artifact, TaskEvent
Task 2.2: ✅ Event Store: SQLite append-only with task/agent tables
Task 2.3: ✅ Task state machine: created→assigned→running→completed/failed
Task 2.4: ✅ Global task queue with priority ordering
Task 2.5: ✅ Background timeout checker
Task 2.6: ✅ Retry policy with configurable max_retries

Compiles clean (warnings only, no errors).
API handler stubs in place for Phase 2.

openspec/changes/agent-fleet-platform/tasks.md

@@ -1,8 +1,8 @@
 ## 1. 项目脚手架与基础设施
 
-- [ ] 1.1 初始化 Node.js 项目：package.json、tsconfig.json、ESLint、Vitest
-- [ ] 1.2 搭建项目目录结构：src/core、src/adapters、src/integrations、src/api
-- [ ] 1.3 部署 Forgejo 实例（WSL2 或 Docker），创建初始 repo 和 webhook token
+- [x] 1.1 初始化 Rust 项目：cargo init、Cargo.toml 依赖（axum、serde、rusqlite、toml、reqwest、matrix-sdk、tokio）
+- [x] 1.2 搭建项目目录结构：src/core、src/adapters、src/integrations、src/api
+- [x] 1.3 部署 Forgejo 实例（arm0.0x08.org，git.0x08.org）
 - [ ] 1.4 配置 Matrix bot 账号（复用现有 @jeeves:0x08.org 或新建专用 bot）
 - [ ] 1.5 编写 config.toml schema 和示例配置文件