docs: document fern generate --pack and --pack-mode

[devin-ai-integration]

Summary

fern generate --pack is a new CLI flag that turns any local-file-system SDK output into the installable package artifact for that language (npm tarball, Python wheel, JAR, .nupkg, gem, Composer zip, crate, Go source zip), written to a fern-dist/ folder inside the output directory. --pack-mode docker runs each language's packaging toolchain inside its official container image, so no host toolchains are required.

This matters for teams that want to hand a generated SDK to internal consumers without publishing to a public registry. Previously the CLI only produced source directories, so someone had to build the artifact by hand with the right toolchain installed.

Pages changed

• fern/products/cli-api-reference/pages/commands.mdx — canonical reference. Adds [--pack] [--pack-mode <mode>] to the fern generate usage line plus ### pack and ### pack-mode sections: per-language artifact table, fern-dist/ location, full-project implication (pyproject.toml, README.md, etc.), aggregated Packaging failed for: ... behavior and empty-dir cleanup, Swift's source-package warning, --runner podman for docker mode, and the rejected combinations (--pack with --preview or --docs, --pack-mode without --pack).
• fern/products/sdks/reference/generators-yml-reference.mdx — one-sentence pointer in the local-file-system output accordion.
• fern/products/sdks/deep-dives/self-hosted.mdx — one-sentence pointer in the "Run generation locally" step.

Go is documented as producing a module source archive rather than a source-distribution warning, per the follow-up fern-api/fern#17293, which shipped in the same CLI release (5.86.0) as #17284.

No changelog entry: this is a CLI/SDK change, not a Docs-product feature.

Verification

• pre-commit run --files <changed files> — Vale passed; no new findings on changed lines.
• cd fern && npx fern-api@5.59.0 check --warnings — 0 errors.

Link to Devin session: https://app.devin.ai/sessions/8e890e1535f64065a937b9f6eee77709

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment, CI, and merge conflict monitoring

[github-actions]

🌿 Preview your docs: https://fern-preview-devin-1785431301-document-fern-generate-pack.docs.buildwithfern.com/learn

Here are the markdown pages you've updated:

• learn/cli-api-reference/cli-reference/commands
• learn/sdks/deep-dives/self-hosted
• learn/sdks/reference/generators-yml

[devin-ai-integration]

Closing as superseded by #6497. fern-api/fern#17307 renamed --pack/--pack-mode to --package/--package-mode with no aliases, so the flags documented here no longer exist. All of this PR's content (the per-language artifact table, the Docker toolchain images, the --preview/--docs incompatibility, and the generators-yml-reference.mdx cross-link) has been ported into #6497 with the new flag names.