chore: import upstream snapshot with attribution

cli-tool/components/skills/development/task-execution-engine/references/task-format.md

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+# Task Format Specification
+
+## Basic Structure
+
+```markdown
+## Implementation Tasks
+
+- [ ] **Task Title** `priority:N` `phase:PHASE` `deps:Dep1,Dep2`
+  - files: file1.py, file2.py
+  - [ ] Acceptance criterion 1
+  - [ ] Acceptance criterion 2
+```
+
+## Task Line
+
+```
+- [ ] **Task Title** `priority:1` `phase:model` `deps:Other Task`
+```
+
+| Component | Required | Description |
+|-----------|----------|-------------|
+| `- [ ]` | Yes | Checkbox (unchecked) |
+| `**Title**` | Yes | Task title in bold |
+| `priority:N` | No | Priority 1-10 (default: 5, lower = higher) |
+| `phase:X` | No | Phase: model, api, ui, test, docs |
+| `deps:A,B` | No | Comma-separated dependency task titles |
+
+## Task Details (Indented)
+
+### Files Line
+
+```markdown
+  - files: src/models/user.py, tests/test_user.py
+```
+
+Comma-separated list of files to create/modify.
+
+### Acceptance Criteria
+
+```markdown
+  - [ ] User model has email field
+  - [ ] Password hashing uses bcrypt
+```
+
+Checkboxes for each acceptance criterion. All must be checked for task to be complete.
+
+### Failure Reason (Auto-added)
+
+```markdown
+  - reason: Database connection failed
+```
+
+Added automatically when task is marked as failed.
+
+## Status Markers
+
+| Status | Checkbox | Marker |
+|--------|----------|--------|
+| Pending | `- [ ]` | (none) |
+| Completed | `- [x]` | ✅ |
+| Failed | `- [x]` | ❌ |
+
+## Priority Order
+
+1. Lower priority number = execute first
+2. Dependencies must be completed first
+3. Tasks with unsatisfied dependencies are "blocked"
+
+## Examples
+
+### Pending Task
+
+```markdown
+- [ ] **Create User model** `priority:1` `phase:model`
+  - files: src/models/user.py
+  - [ ] User model has email and password_hash fields
+  - [ ] Email validation implemented
+```
+
+### Completed Task
+
+```markdown
+- [x] **Create User model** `priority:1` `phase:model` ✅
+  - files: src/models/user.py
+  - [x] User model has email and password_hash fields
+  - [x] Email validation implemented
+```
+
+### Failed Task
+
+```markdown
+- [x] **Create User model** `priority:1` `phase:model` ❌
+  - files: src/models/user.py
+  - [ ] User model has email and password_hash fields
+  - reason: bcrypt package not installed
+```
+
+### Task with Dependencies
+
+```markdown
+- [ ] **Create auth API** `priority:3` `phase:api` `deps:Create User model,Implement JWT`
+  - files: src/api/auth.py
+  - [ ] POST /register endpoint
+  - [ ] POST /login endpoint
+```
+
+This task will not be selected by `next` until both "Create User model" and "Implement JWT" are completed.