feat: dual execution model (SSH CLI + HTTP pull)

- ExecutionMode enum: SshCli (orchestrator dispatches) | HttpPull (agent pulls)
- SSH CLI executor: spawn remote agents via ssh + CLI template
- Local subprocess as SSH special case (localhost)
- HostConfig with capability matching and load-based selection
- Dispatch loop: scan created tasks → select host → execute → update
- CliAdapterConfig: CLI templates for Codex and Claude Code
- Structured prompt construction (Issue → goal/constraints/validation)
- Output parsers: Codex JSON, Claude Code JSON, raw fallback
- TaskStatus::ReviewPending + review_count loop limit
- Forgejo webhook: pull_request (opened→review_pending, merged→completed)
- Forgejo webhook: push events (task/* branch → last_activity_at)
- HTTP API: dequeue only returns http_pull tasks
- HTTP API: status update only for http_pull mode
- Token auth config for http_pull agents
- Adapter module rewritten: AgentAdapter trait removed → config-driven CLI templates
- New fields: execution_mode, assigned_host, branch_name, pr_title, last_activity_at, review_count
- 30/30 tests pass

openspec/changes/adapter-cross-machine-revision/specs/notification-via-forgejo/spec.md

@@ -0,0 +1,44 @@
+## ADDED Requirements
+
+### Requirement: Git branch as task execution unit
+每个任务 SHALL 关联一个 Git 分支。Agent 在该分支上工作，通过 PR 提交结果。分支命名约定：`task/{task_id}`（例如 `task/org%2Frepo%2342`）。
+
+#### Scenario: Agent creates branch for task
+- **WHEN** Agent 领取任务 org/repo#42
+- **THEN** Agent SHALL 在目标仓库创建分支 `task/org%2Frepo%2342`（基于 master/main）
+
+#### Scenario: Agent pushes commits to task branch
+- **WHEN** Agent 执行过程中产生代码变更
+- **THEN** Agent SHALL 推送 commit 到对应的 task 分支
+
+### Requirement: PR webhook as completion notification
+Agent 完成任务后 SHALL 在 Forgejo 创建 Pull Request。Forgejo 的 PR webhook 触发 Orchestrator 状态更新，替代不可靠的直接通知。
+
+#### Scenario: Agent creates PR → Orchestrator receives webhook
+- **WHEN** Agent 为任务 org/repo#42 创建 PR
+- **AND** Forgejo 触发 `pull_request.opened` webhook
+- **THEN** Orchestrator SHALL 收到 webhook，识别 PR 标题或分支名中的 task_id
+- **AND** 将任务状态更新为 `review_pending`（等待 receipt 验证）
+
+#### Scenario: PR merged → receipt auto-validated
+- **WHEN** PR 被 merge
+- **AND** Forgejo 触发 `pull_request.merged` webhook
+- **THEN** Orchestrator SHALL 自动将任务状态转为 `completed`，生成 receipt
+- **AND** 在对应 Issue 添加评论：`✅ Task completed — PR #15 merged`
+
+### Requirement: Task branch and PR naming convention
+Orchestrator SHALL 在任务详情中返回预期的分支名和 PR 标题格式，供 Agent 使用。
+
+#### Scenario: Task detail includes branch info
+- **WHEN** Agent 查询 `GET /api/v1/tasks/org/repo#42`
+- **THEN** 返回 JSON SHALL 包含 `branch_name` 和 `pr_title` 字段
+- **AND** `branch_name` 格式为 `task/{url_encoded_task_id}`
+- **AND** `pr_title` 格式为 `feat: {issue_title} (#{issue_number})`
+
+### Requirement: Push events as progress tracking
+Forgejo push webhook SHALL 作为 Agent 工作进度的间接信号。
+
+#### Scenario: Agent pushes to task branch
+- **WHEN** Forgejo 触发 `push` webhook，目标分支匹配 `task/*` 模式
+- **THEN** Orchestrator SHALL 记录该 push 事件作为任务进度信号
+- **AND** 更新任务的 `last_activity_at` 时间戳