Keep nix mirror 101 zig langtools (#19)

* port(src/ui/tea/gsa_gui.affine): ReScript surface -> AffineScript (Refs #229)

Oracle-validated Tier-1 port (affinescript main @ #229 canonical map,
docs/RESCRIPT-ELIMINATION.adoc):
- List(T) -> [T]  (1 occurrence)
- expression-position record literals { ... } -> #{ ... } (the record
  sigil, spec.md:414-421). Match record-PATTERNS and struct/enum/type
  decl bodies correctly left as { } (sigil is expression-literal-only,
  oracle-confirmed).
- ReScript string `+` -> AffineScript `++` where present (concat is
  `++`; `+` is numeric — left a String/Int unify error beneath the
  parse wall; numeric `+`/`-` untouched).

Verified: `affinescript main check src/ui/tea/gsa_gui.affine` -> Type checking passed
(was: parse error / DRIFT-SYNTAX pre-port). Self-contained file, no
imports. Refs #229 (estate-wide, sequenced, human-gated — not Closes).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* docs(flake): annotate KEEP+DEP rationale per standards#102 rule 3

Per the campaign gate, this flake is LOAD-BEARING — guix.scm has real
build phases (Zig build + install) but declares empty
`(native-inputs (list))` / `(inputs (list))`, with `zig` commented as
"uncomment when available in Guix". The flake's devShell is the sole
source of the language layer (zig, zls, idris2) and the RSR-template
common dev tools (git, just, nickel, curl, bash, coreutils).

Top-comment now states the dep gap.

Refs standards#101 standards#102.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: hyperpolymath <hyperpolymath@users.noreply.github.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath