chore: pin forge-cli 0.28.0, and mark what shipped in it - #201

Pins the site to data-product-forge 0.28.0 (on PyPI since 2026-11-06) and marks what shipped in it.

• cli-version.json and the 14 version claims the sweep flags move to 0.28.0. The stable schema stays 0.7.6 and the quickstart scaffold stays 0.7.5, as the 0.28.0 CLI reports. No schema changed, so the regenerated contract reference pages differ only in their version line.
• Every "On forge-cli main, not yet in a release" marker for forge-cli #828, #830, #832, #833, #836 and #837 becomes *(since 0.28.0, …)*. The sentences written ahead of the install change now describe it as released.
• docs/upgrading.md gains Changes in 0.28.0, in this order:
  • the install change: [standard], [litellm] (alias [ai]), [mcp], [lineage] and [aws], and which commands stop before doing work;
  • the changed pins;
  • the dependency list (#829);
  • the Debezium Server dotenv names (#833);
  • the Iceberg catalogAuth checks (#828, #830);
  • Databricks comments, tags, certification and refusal codes (#831, #835);
  • the fluid publish location (#840), and the rest.
• scripts/forge-cli-releases.json is reviewed through 0.28.0.

Checks

• Against data-product-forge==0.28.0 from PyPI (Python 3.11), all exit 0:
  • check_cli_docs.py
  • check_providers.py
  • check_cli_docs.py --markers-only
  • gen_contract_reference.py --check
• npm ci && npm run docs:build && node scripts/check-dist-links.mjs: exit 0.
• A reviewer ran the 0.28.0 base-install CLI on every changed claim (install lines, stop-before-work messages, fluid doctor, the dotenv names), and its corrections are applied. They were: the #823 marker (that PR shipped in 0.27.0), the exact JMX_* names, the hedged Databricks ASSIGN requirement, the narrower AWS account-id failure, the doctor notice condition, and the fluid ai setup and fluid forge provider wording.

Not covered

docs/providers/databricks.md does not yet describe the 0.28.0 Unity Catalog comments, tags and certification beyond the upgrading summary, and the new databricks-* codes are not yet in docs/advanced/error-codes.md. That needs its own page update.