M11 release

[tamnd]

Part of #10. Spec: notes/Spec/3007/*.md.

The README stops claiming things that are not true, and v0.3.0 ships.

Why

Two claims on the front page are false today: that Amazon marks up JSON-LD, and that amz is one pure-Go binary.

Checklist

• README rewritten against measurements: no JSON-LD claim, and "one pure-Go binary" becomes true
• CHANGELOG with the breaking changes section from the spec verbatim
• A migration note for --cookies, --workers, the record shape, and the four commands that now return less
• Weekly live drift job running amz verify --live --strict
• govulncheck clean
• The seven commands in the spec's acceptance list all return records against live amazon.com
• The docs site rewritten for v0.3.0: it still documents the flat record, --cookies, --workers and a duckdb dependency
• Tag v0.3.0, ten platforms, checksums

Done when

The checklist above is ticked, go test ./... is green, and the matching block in #10 is ticked with a comment naming the PR.