review: include the oasdiff version and platform in the encrypted review bundle (#1113)

* docs: point the online catalog link to /docs/breaking-changes

The /checks filter page is retired; oasdiff.com/docs/breaking-changes is the
canonical online catalog. Repoint the two 'browse the full catalog' links.

* review: include the oasdiff version in the encrypted bundle

Add ToolVersion (build.Version) to review.Payload, set by the CLI when it builds
the --open bundle. It travels inside the encrypted bundle, so the review page can
tell when a review came from an outdated oasdiff and nudge an upgrade. The GitHub
Action inherits it automatically: it runs this same CLI with --open (free path
and Pro --review-token path both go through here). Empty for bundles from older
clients that predate the field.

Round-trip covered by TestPayloadEncrypt_RoundTrip.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* review: also include the platform (github-action vs CLI) in the bundle

Add Platform to review.Payload, set from the PLATFORM env var: 'github-action'
when the CLI runs inside the oasdiff GitHub Action (which sets it in its image),
empty for a plain CLI invocation. Lets the review page tailor an upgrade nudge
(bump the action vs set up the action). No action change needed; the env already
exists. Round-trip covered by TestPayloadEncrypt_RoundTrip.

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Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>