Add Alexandria CLI terms commands and release beta.13

[developersdigest]

Adds explicit provider terms discovery and acceptance through the new /exchange/provider-terms/accept endpoint. Acceptance requires the reviewed version, digest, and --confirm; errors are preserved without automatic retries. Terms-required execution errors point users to the commands.

Includes the already-published beta.12 progressive category/provider/tool browsing changes and bumps the Alexandria package to 1.23.4-alexandria-beta.13.

Validation: TypeScript build and 26 focused tests pass. Acceptance requests are mocked; no live terms were accepted. The terms catalog can still be gated for some teams even though the acceptance endpoint is available.

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Summary by cubic

Adds explicit provider terms discovery and acceptance via new alexandria terms commands, so users can review and confirm terms before running provider commands that require them.

• terms accept posts to /exchange/provider-terms/accept and requires the reviewed --version, --digest, and --confirm; it never retries and preserves errors like 409 terms_changed.
• Execution errors with THIRD_PARTY_DATA_TERMS_REQUIRED now point users to the terms commands.
• Adds progressive category/provider/tool browsing with alexandria <category> shortcuts and --contracts expansion.
• The terms catalog may remain access-gated even when the acceptance endpoint is available.
• Bumps the package to 1.23.4-alexandria-beta.13.

^{Written for commit 00eb1ca. Summary will update on new commits.}