feat: add grouped weekly and monthly tables

[jiunbae]

What changed

• replace the compact fleet output with a ccusage-style Unicode table
• add --group-by agent, --group-by device, and --group-by none
• show model lists, full token counts, costs, date totals, and a final total row
• support daily, weekly, and monthly reports through one aggregation pipeline
• preserve --by-host and --no-by-host as compatibility aliases

Why

The initial device-first compact rows were difficult to scan and did not match ccusage's native report shape. Users also need to choose whether the primary breakdown is the agent or the device.

Validation

• npm run check
• npm test (15 tests)
• daily grouped by agent and device against 4/4 configured hosts
• weekly grouped by agent against 4/4 configured hosts
• monthly grouped by device against 4/4 configured hosts
• npm pack --dry-run