docs: stdlib API reference (end-user depth gap)

[hyperpolymath]

Audience

End users (people writing AffineScript).

Gap

Surfaced by the 2026-06-21 docs-depth gap-assessment (end-user / developer / maintainer triple). The onboarding ramp is now good — audience router (#649), tutorial lessons 1–10, docs/guides/warmup/ — but end-user docs stop at setup/basics. There is no canonical API reference for the stdlib that ships today: wiki/stdlib/overview.md is a single overview page with no per-module/per-function signatures, semantics, or examples.

This is distinct from:

• docs/standards/stdlib-roadmap.adoc — what to build (roadmap), not how to use what exists.
• [campaign] AffineScript top-50 framework bindings roadmap (UMBRELLA) #446 (top-50 framework bindings campaign) — bindings to external frameworks, not reference docs for the core stdlib surface.

Suggested scope

• docs/reference/stdlib/ (.adoc per repo DOC-FORMAT), one page per public stdlib module (stdlib/*.affine — e.g. Deno, Http, Crypto, Network, Sqlite, plus the core prelude).
• Each page: function signatures + one-line semantics + at least one verified runnable example (check/eval).
• Ideally generated/cross-checked from extern declarations and docs/STDLIB-EXTERN-AUDIT.adoc so it can't drift from the compiler.
• Link from the README/NAVIGATION.adoc audience router and wiki/stdlib/overview.md.

Acceptance

Every public stdlib module has a reference page with signatures and ≥1 verified example, reachable from the audience router.