fix(cli): replace retired Basic Memory links

[phernandez]

Why

The link fixes proposed in #1026 are valid, but that external-contributor PR remains blocked on the CLA. This is an independent maintainer implementation; no contributor commit was copied.

The retired documentation paths and subscription URL return 404s. The CLI also retained the retired subscription URL as its fallback when the cloud API omits a subscribe_url.

What changed

• update the README knowledge-format and CLI-reference links to their canonical documentation paths
• update the cloud CLI guide to use the pricing page
• update the CLI subscription-required fallback to use the pricing page
• add a regression test for the missing-subscribe_url fallback

Server-provided subscription URLs still take precedence.

Validation

• uv run pytest tests/cli/test_cloud_authentication.py -q — 10 passed
• just fast-check
• verified the three replacement URLs return HTTP 200

Risk

Low. The runtime change only affects the fallback URL when the cloud API does not provide one.

Supersedes #1026.

[phernandez]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Delightful!

Reviewed commit: 1caa5c1f90

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