Add a usage reader for Goose (Block / Linux Foundation)

[toshipepe]

Bring Goose into Tokimeter's local-first usage meter using the established reader pattern.

What's needed:

1. Locate Goose's local usage store and capture a scrubbed schema fixture.
2. Add a pure reader plus a collectGooseUsageEvents walker.
3. Gate collection on --tool goose.
4. Add fixture coverage and a no-content/no-PII test when usage metadata is co-located with conversation content.
5. Add Goose to the README support table with an honest verification level.

Rules: metadata only, no extra model calls, and honest ~$ estimates. See CONTRIBUTING.md. A documented finding that Goose has no usable local usage data is also a valid close.