The terminal's usage screen says what the crew's tokens bought: dollars, runs, changes landed and cost per change, as MCP `returns` does #7271

For: the owner deciding whether the crew is worth its spend, from the terminal. Steering needs the return next to the cost.

readReturns is reached from MCP returns (src/http/mcp/tools/returns.ts). The terminal's usage screen (src/tui/screens/usage.ts) shows usage but not what it bought.

Done:

• [ ] The usage screen has a returns block over the last 7 days: dollars, runs, changes landed, cost per change; [/] move between 1, 7, 30 and 90 days.
• [ ] On a repository's usage, it narrows to that app, as repo does in MCP.
• [ ] Someone MCP would refuse sees no returns block.
• [ ] A test in test/tui-usage*.test.ts or a new one: seeded runs and landed pulls give the right numbers for 7 and 30 days; no runs reads "nothing spent" in words, not NaN.

Files: src/tui/screens/usage.ts, one test. Risk: low.