ESC-03: no stdlib Map/Dict type — Dict.t port target (Refs 229, 160/162)

[hyperpolymath]

Problem

ReScript Dict.t<v> (string-keyed map) has no stdlib target:
stdlib/collections.affine is list operations only; there is no Map/Dict
type. stdlib/Http.affine:16 already flags this gap (Dict<String,String>,
tied to #160/#162). 6 estate .affine files carry Dict.t (post-#228
re-audit; docs/RESCRIPT-ELIMINATION.adoc Tier-3 ESC-03).

Escalated language-side (bidirectional-evidence discipline, as #228).

Ask

A canonical stdlib Map/Dict type with the minimal surface #229 needs
(make/get/set/fromArray/iteration). Coordinate with #160/#162 — the
Http.affine Dict gap and this are the same need.

Context

• Blocks the Tier-3 slice of ESTATE: total ReScript-surface elimination from all .affine (committed goal; blocked-on #228) #229; intersects stdlib: portable Http.fetch (body/headers/methods/response) #160/stdlib: Dict / Map primitive (keyed associative container) #162.
• Refs ESTATE: total ReScript-surface elimination from all .affine (committed goal; blocked-on #228) #229. Reproducer: tools/estate-rs-audit/.