feat(lang-core): generate prompts from a subset of the library (componentAllowlist)

[Shinyaigeek]

Closes #633.

Problem

library.prompt() always emits every component in the library. For a library with ~54 components that's ~20k tokens, even when a given screen only needs a handful (e.g. Card / Table / LineChart). That bloats the prompt and — with more component choices — lowers selection accuracy for smaller models. It's especially painful on the CLI / coding-agent path, where the generated prompt stacks on top of the agent's own context.

Solution

An opt-in componentAllowlist on PromptOptions:

library.prompt({
  componentAllowlist: {
    components: ["Card", "Table", "LineChart"],
    includeDependencies: false, // optional, default: true
  },
});

• componentAllowlist.components — when set, only these components appear. Omit componentAllowlist for today's behavior (all components). Fully backward-compatible.
• The prompt's root is always kept, even if not listed, so the output stays self-consistent.
• Sub-component dependencies are pulled in automatically — the transitive closure over the schema refs the library already tracks, so the prompt never references a signature it doesn't show. The root is kept but not used as a closure seed (roots typically render every component, which would defeat the subset). includeDependencies: false opts out and emits exactly the listed components plus root.
• componentGroups are filtered to the kept set; empty groups are dropped.
• Unknown names fail fast with an Available components: ... message, matching the existing root validation.

includeDependencies lives inside componentAllowlist so it can't float as a standalone flag and the dependency it controls is unambiguous.

CLI

openui generate ./lib.tsx --component-allowlist Card,Table,LineChart
openui generate ./lib.tsx --component-allowlist Card,Table --no-include-dependencies

Works for user-defined components too — there's no builtin/custom distinction; it operates on whatever was passed to createLibrary().

Verification

• 6 new unit tests (subset filtering, dependency auto-include, includeDependencies: false, group filtering, unknown-name error, unset default); full lang-core suite passes (79).
• End-to-end against the real ~54-component openuiLibrary: full prompt ≈ 20,340 chars; --component-allowlist Card,Table,LineChart --no-include-dependencies drops it to ≈ 9,274.
• Lint + build clean for lang-core and the CLI. Docs updated (system-prompts.mdx, cli.mdx).

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