[deevus]

Summary

Adds gdzig-zlint (ZLint 0.10.0 with the gdzig CODE_STYLE rules) and wires it
into mise and CI. Follow-up to gdzig/gdzig#290.

• Installs github:gdzig/gdzig-zlint 0.6.1 through mise.toml.
• Adds zlint.json unchanged from the 0.6.1 template. The gdzig rules,
  gdzig-public-docs, and line-length retain their template warn levels;
  homeless-try retains its error level.
• Adds mise run lint and a Lint workflow alongside the existing Tests workflow.
• Applies the rules across the tree: no source edits were needed; safe --fix made no changes.
• No hook system exists in this repo, so none was added.

Verification

• gdzig-zlint .: 0 errors, 9 warnings (before: 0 errors, 9 warnings).
• mise run lint: passes with the same 0 errors and 9 warnings.
• zig build test using Zig 0.14.1: passes; the baseline on main passed too.
• zig fmt --check .: passes before and after; no Zig source files changed.
• Remaining warnings: eight line-length warnings in src/oopz.zig on long
  compile-error messages and expressions, plus one gdzig-public-docs warning
  on build.zig's public build function. They were left to avoid unrelated
  message/logic restructuring or inventing documentation for this lint-only rollout.

Notes

• --deny-warnings is intentionally not enabled yet because the existing
  documentation and line length diagnostics still need cleanup.

Pre-existing CI failures

The Tests workflow's master matrix and the build-docs job fail on this branch.
Neither is caused by this change: the diff only adds mise.toml, zlint.json, and
.github/workflows/lint.yml, and touches no Zig source. The failure is the new
ambiguous-operator error in src/oopz.zig:177, reported by Zig master
0.18.0-dev.567:

src/oopz.zig:177:35: note: in zig 0.17.x, this was evaluated as (... and ...) or ...

main last ran CI on 2026-09-23 with a Zig master that did not yet report this
diagnostic. Reproduced locally on an unmodified main checkout with the same
zig 0.18.0-dev.567+7f0281900 binary: zig build test and
zig build docs --release=fast both fail with the identical error. The new
gdzig-zlint job passes.