init: OpenSpec project scaffolding with proposal, design, specs, tasks

- 7 capabilities: agent-registry, task-router, receipt-protocol,
  forgejo-integration, matrix-chatops, agent-adapter, orchestrator-core
- Tech stack: Rust + axum + zigbuild (single binary)
- Forgejo as task source of truth
- Matrix as real-time ChatOps layer
- Adapter pattern for multi-agent type support

openspec/changes/agent-fleet-platform/specs/matrix-chatops/spec.md

@@ -0,0 +1,45 @@
+## ADDED Requirements
+
+### Requirement: Matrix room as coordination channel
+Orchestrator SHALL 使用 Matrix 房间作为实时协同通道：Agent 状态变更、任务分配、完成通知、人类审批等事件 SHALL 推送到 Matrix。
+
+#### Scenario: Task assigned notification
+- **WHEN** 任务 #42 被分配给 Agent `worker-03`
+- **THEN** Matrix 协同房间 SHALL 收到通知：`📋 #42 → worker-03 [code:typescript]`
+
+#### Scenario: Agent offline alert
+- **WHEN** Agent `worker-03` 连续 3 次心跳失败
+- **THEN** Matrix 房间 SHALL 收到告警：`⚠️ worker-03 offline — 2 running tasks affected`
+
+### Requirement: Slash commands for orchestration
+人类 SHALL 能通过 Matrix slash command 触发编排操作。
+
+#### Scenario: /fleet status
+- **WHEN** 人类发送 `/fleet status`
+- **THEN** Bot SHALL 回复所有 Agent 当前状态表格：Agent ID、类型、状态、当前任务数、能力
+
+#### Scenario: /assign command
+- **WHEN** 人类发送 `/assign worker-03 #42`
+- **THEN** 任务 #42 SHALL 被手动分配给 worker-03
+
+#### Scenario: /retry command
+- **WHEN** 人类发送 `/retry #42`
+- **THEN** 失败的任务 #42 SHALL 被重新入队
+
+### Requirement: Matrix notifications for receipts
+每个 receipt 回写 SHALL 触发 Matrix 通知，包含任务状态、摘要、artifact 链接。
+
+#### Scenario: Task completed notification
+- **WHEN** 任务 #42 的 receipt 验证通过，状态为 `completed`
+- **THEN** Matrix 房间 SHALL 收到通知：`✅ #42 completed by worker-03 — PR #15 — "修复登录验证 bug"`
+
+#### Scenario: Task failed notification
+- **WHEN** 任务 #42 失败
+- **THEN** Matrix 房间 SHALL 收到通知：`❌ #42 failed — worker-03 — "构建超时"`
+
+### Requirement: Per-agent Matrix thread
+每个 Agent SHALL 有独立的 Matrix thread（或 topic），用于该 Agent 的执行日志、状态更新、调试输出。
+
+#### Scenario: Agent execution log
+- **WHEN** Agent worker-03 开始执行任务 #42
+- **THEN** worker-03 的 thread SHALL 收到执行开始消息，后续日志更新也在此 thread