[Feature]: Explicit task dependency declarations in tasks.md to enable parallel execution

[wakita181009]

Problem Statement

The default tasks-template.md lists tasks sequentially with no dependency metadata. Agents cannot determine which tasks are independent and safe to run concurrently.

Proposed Solution

Add three constructs to the tasks template:

1. (depends on ...) suffix on each task

- [ ] T001 Create project structure                                                                                                                                              
- [ ] T002 Initialize project with dependencies (depends on T001)                                                                                                                  
- [ ] T003 Configure linting tools (depends on T001)

Tasks with no dependencies omit the suffix. This is required for any task that depends on another.

2. Dependency DAG section at the bottom of tasks.md

## Dependencies & Execution Order                                                                                                                                                
                                                                                                                                                                                   
Wave 1: T001                   (no deps)                                                                                                                                         
Wave 2: T002, T003             (T001 done → parallel)                                                                                                                              
Wave 3: T004, T005, T006       (T002 done → parallel agents)                                                                                                                       
...

Alternatives Considered

No response

Component

Spec templates (BDD, Testing Strategy, etc.)

AI Agent (if applicable)

None

Use Cases

No response

Acceptance Criteria

No response

Additional Context

Why

• /implement can schedule tasks optimally instead of strict sequential execution
• /taskstoissues can generate GitHub Issues with "blocked by" references