Add an ad-hoc task to an existing project plan
# Add Task
Add a single task to an existing project's pending queue without going through full planning process.
## Usage
If project is omitted, will prompt to select from existing projects in `.plans/`.
## Your Task
Create a new task file in `.plans/<project>/pending/` based on the description: "${{{ARGS}}}"
### Step 1: Parse arguments
Extract project name and task description from args.
- If project name included (first arg matches existing .plans/<project>/ directory), use it
- Otherwise, list existing projects and ask user to specify which one
- Remaining args are the task desc...