Complete the per-language testing guides (Zig, BEAM, proofs) + Julia refresh + AffineScript SSOT

[hyperpolymath]

Child of #460. Wave 5 (#459) shipped language-testing-standards.md v2.0.0 (RFC-2119 R1–R9), the guide template, the AffineScript guide, and the check-language-guide.sh gate. This tracks filling out the required set.

Each is a straightforward fill of standards/templates/language-testing-guide-TEMPLATE.md — a requirement-mapping table (concrete tool or visible none), tools, a SHA-pinned CI pipeline, best practices, and an honest "Known gaps" section. scripts/check-language-guide.sh enforces the structure.

• Zig — zig-testing-guide.md (estate default for APIs/FFI/gateways/SDKs; zig build test, zig fmt).
• Elixir + Gleam (BEAM) — one guide covering ExUnit / PropCheck / ExCoveralls / Credo and gleeunit.
• Idris2 / Agda (proofs) — totality/--check, ECHIDNA proof gate; ties to proof-debt epic Epic: estate proof-debt remediation (2026-05-18 reconciled audit) #124.
• Julia refresh — bring julia-testing-tools-guide.md (v1.0.0, 2024) onto the R1–R9 mapping and flip its "not yet integrated" rows.
• AffineScript SSOT migration — move affinescript-testing-guide.md to hyperpolymath/affinescript (canonical), leaving a registry pointer here. Flip R3 to blocking once affinescript-verify.yml is reliably green.

Acceptance: each new guide passes just language-guides-check; the required-set table in language-testing-standards.md shows all present.