mise.toml declares zig = "latest" while .tool-versions pins 0.16.0 and the gate rejects skew #46

Surfaced by review on PR #42 (Codex finding on AFFIRMATION.adoc).

mise.toml:12 has zig = "latest"; .tool-versions:10 has zig 0.16.0; tests/e2e/invoke_slice.sh hard-fails on any version other than the .tool-versions pin. A developer who lets mise resolve zig@latest gets a compiler the gate immediately refuses, so the repository's toolchain is not consistently pinned. The AFFIRMATION now says so in its toolchain row.

Fix: pin zig = "0.16.0" in mise.toml (or remove the zig line there and let .tool-versions be the single source), matching CI's mlugg/setup-zig pin. One line; owner or a CI pass — not in #42, which is a status-surface pass.