docs(cli-generator): document the --schema flag

[fern-api]

Summary

Every generated Fern CLI has a --schema flag that prints its whole command surface as JSON, so an agent (or a human) can learn what commands and flags exist without parsing --help prose. This PR documents that flag, including the newly added per-property flag field: each property in an operation's input now states the exact flag to pass. That matters because the flag often isn't the property's name from the spec — headers are kebab-cased, a spec name that collides with a global flag such as --query gets a -param suffix, and x-fern-parameter-name can rename it. With flag in the contract, a valid invocation can be built straight from --schema instead of re-deriving the CLI's naming rules.

Implements docs for:

• disclose the flag name for every property in --schema (fix(cli-generator): disclose the flag name for every property in --schema fern#17554) — fix(cli-generator): disclose the flag name for every property in --schema fern#17554

Pages changed:

• fern/products/cli-generator/schema.mdx — new page covering the three scopes (<bin> --schema, <bin> <resource> --schema, <bin> <resource> <method> --schema), the root object (globalFlags, sdkVariables, operations), the per-operation contract (input, output, defaultSelection, paginable, binaryResponse, streaming), property metadata, and jq recipes. Property metadata leads with flag, explains the three reasons it differs from the property key, notes that multipart/form-data fields carry it too, and that a property with no flag is reachable only through --params / --json.
• fern/products/cli-generator/features.mdx — links to the new page, and the flag-name guidance now covers both directions: --help shows the spec name as (api: <name>), --schema keys by that name and gives the flag in flag.
• fern/products/cli-generator/overview.mdx — "Runtime introspection" card links to the page.
• fern/products/cli-generator/cli-generator.yml — navigation entry.

Content verified against the generator implementation (resolve_param_flag_name / resolve_multipart_field_flag_name in generators/cli/sdk/src/openapi/) and real output from a generated CLI.

Link to Devin session: https://app.devin.ai/sessions/f3f5bc50b2b648d5b47ba5a67fc3d665
Open in Devin Desktop: https://app.devin.ai/desktop/session/f3f5bc50b2b648d5b47ba5a67fc3d665?variant=devin

[fern-api]

Requested by: will.kendall
Slack thread: View conversation

[github-actions]

🌿 Preview your docs: https://fern-preview-fern-document-schema-flag.docs.buildwithfern.com/learn

Here are the markdown pages you've updated:

• learn/cli-generator/get-started/features
• learn/cli-generator/get-started/overview
• learn/cli-generator/get-started/schema