fix(ci): restore missing build.zig — CI fails at step one on every run

[gHashTag]

Problem

CI / Build & Test has failed 12 out of the last 12 runs, always at the very first step:

zig build author-guard -Dci=true
error: no build.zig file found, in the current directory or any parent directories
##[error]Process completed with exit code 1

Because it dies immediately, every genuine problem in the build, tests, format check and schema drift gates is invisible — the workflow never reaches them. This masked five separate site-deploy defects I only found by inspecting runs one at a time (#611, #612, #614).

Cause

main has no build.zig, while it does have:

• build.zig.zon (the Zig package manifest) at the root
• ~2815 .zig sources, including everything ci.yml references (src/vm.zig, src/trinity.zig, src/tri/job_system.zig, .trinity/registry.json)

So this is a Zig project root missing only its build script. build.zig still exists on other branches — including every dependabot branch, which forked from an older main — which points at the cleanup/git-history-reduce-6gb-to-220mb history rewrite as where it was dropped.

Change

Restored build.zig from cleanup/git-history-reduce-6gb-to-220mb.

⚠️ Honest caveat — please look before merging

That branch is dated 2026-03-18; main is at 2026-08-05. The restored build script may not match five months of source changes, so CI may now fail differently — at a real error rather than at a missing file. That is still progress, but it is not automatically "fixed".

I deliberately did not verify locally: my toolchain is Zig 0.16 while CI pins 0.15.2, so a local result would be measured with the wrong instrument and could mislead. The authoritative check is this PR's own CI run.

Decision rule: if Build & Test gets past the author-guard step, this is a net improvement and worth merging (with follow-up for whatever it now reveals). If it fails in a way that suggests the wrong build script, the right fix is to commit the current build.zig from your working tree instead — you have one there, tracked on feat/tri-net-skill-radio-ops.

🤖 Generated with Claude Code