docs: the extras each AI, MCP and lineage feature needs (forge-cli 0.28.0; merge at release) - #200

Draft. It waits for the forge-cli 0.28.0 release; merge it when 0.28.0 ships. Every new sentence is already marked On forge-cli main, not yet in a release, so an early merge would not mislead 0.27.0 readers. The marker sweep still has to be tidied at the release pin bump.

What

Docs for what landed on forge-cli main after 0.27.0. All three PRs are merged on main and not released:

• forge-cli #837: litellm, mcp and openlineage-python leave the base install. The base install drops from 88 to 41 packages on Linux Python 3.12, 86 to 45 on Linux 3.10, and 89 to 40 on Windows 3.12.
• forge-cli #836: lazy command imports. fluid --help loads about 300 modules instead of about 857.
• forge-cli #832: nine internal modules that nothing imported are removed.

docs/upgrading.md rewrites the planned-change section to what landed:

• a table of which command needs which extra;
• the fail-before-work behaviour, with real error output;
• the keyless alternatives each message names;
• the [aws] note and the pins.

Pages that tell readers to use an AI, MCP or lineage feature now name the extra it needs: cli/forge, cli/ai, cli/init, cli/mcp, cli/scaffold-ide, cli/doctor, advanced/{mcp,llm-providers,litellm-backend,forge-copilot-discovery,production-troubleshooting,environment-variables,source-aligned-acquisition}, concepts/quality-sla-lineage, providers/aws, forge-data-model, two walkthroughs, getting-started, faq and README.

Install lines use extras that already exist in 0.27.0, so they are right on both versions.

Checked against

• forge-cli main 98729252 (#837), with the changelog correction #838 (029e8f4d).
• A verifier ran the CLI on a bare install (no litellm, mcp or openlineage) and a full install at that commit. Seven imprecise claims are fixed in 39cccd3:
  • forge data-model needs litellm only with an API-key provider;
  • fluid init falls back to template mode instead of exiting;
  • lineage is emitted only through OpenTofu apply and acquisition builds;
  • the 0.27.0 litellm floor is 1.83.14;
  • which alternatives each message names;
  • mcp-sampling works only inside fluid mcp serve;
  • plan, validate and generate iac run without boto3.
• Local checks on Python 3.11, against the pinned CLI 0.27.0:
  • scripts/check_cli_docs.py (all checks; FORGE_CLI_CHANGELOG was pointed at main's CHANGELOG);
  • scripts/gen_contract_reference.py --check;
  • npm ci && npm run docs:build && node scripts/check-dist-links.mjs.