fix: create default config when missing instead of crashing (closes #2)

[chengfei-gh]

Fix for #2: Crash when config file missing

Problem

python task.py list crashes with FileNotFoundError when ~/.config/task-cli/config.yaml doesn't exist.

Solution

load_config() now automatically creates a default config file if missing:

• Creates ~/.config/task-cli/ directory if needed
• Writes sensible defaults matching config.yaml.example
• Prints helpful message: [task-cli] Created default config at ...

Changes

• Modified load_config() in task.py with graceful config creation
• Added DEFAULT_CONFIG constant with default settings

Testing

# Remove config and verify no crash
rm -rf ~/.config/task-cli/
python task.py list   # Creates default config, lists tasks (empty)

# Verify default config was created
cat ~/.config/task-cli/config.yaml

Acceptance Criteria

• No crash when config file is missing
• Creates sensible default config
• Shows clear message about config creation
• All existing tests pass

Payment

Solana wallet: CZkLs4m55JBffoowGUtyfqb5GrymUVxgr9kMTrXKfbJV