## Why

The current renderer shows three quota rows (5-hour, 7-day, month), but the monthly window is an awkward fit: the API only returns `max_flows` and `max_value_usd` for it — no `used_*` fields — so the monthly progress bar is always empty and the used columns show `—`. Visually this looks like a bug or missing data. Since the monthly row is really just a cap/limit rather than a live-usage window, it belongs below the usage bars as a compact one-liner, not as a peer row next to the two real progress windows.

## What Changes

- Drop the `month` row from the three-progress-bar block. The renderer now shows only the `5 hour` and `7 day` rows with bars.
- Add a compact "Monthly cap" summary line below the "Tokens consumed" line, formatted as `Monthly cap: <max_flows> flows · $<max_value_usd>` (e.g. `Monthly cap: 34560 flows · $1134.33`).
- Update the human-mode snapshot tests and the README ASCII sample accordingly.
- No change to JSON output — `quota_monthly` is still passed through in the API response verbatim.

## Capabilities

### New Capabilities
<!-- None — this is a behavior change to an existing capability. -->

### Modified Capabilities
- `subscription-usage`: the "Render three quota windows per account" requirement becomes "Render two quota windows per account"; the "Display token USD value consumed per account" requirement's prose is adjusted from "three quota rows" to "quota rows"; a new "Display monthly cap" requirement is added.

## Impact

- `internal/render/render.go` — remove the `month` entry from the progress-bar row builder; add a new line emission after the tokens-consumed line.
- `internal/render/render_test.go` — drop the `— / 34560 flows` and ` n/a` assertions; add an assertion for the new `Monthly cap:` line.
- `README.md` — update the ASCII sample to reflect two progress bars plus the monthly cap line.
- No API, config, or CLI-flag changes; no effect on exit codes or JSON mode.