[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-specific rules
  are warn in this template; homeless-try is error.
• Adds mise run lint and a Lint workflow for pushes to main and PRs.
• Applies the trailing-comma autofix to build.zig. No other source changes.
• No hook system exists in this repo, so none was added.

Verification

• gdzig-zlint .: 0 errors, 1 warning (before: 0 errors, 2 warnings).
• mise run lint: succeeds with the same remaining warning.
• Zig 0.15.1 zig build: fails on both this branch and main before compilation:
  build.zig.zon contains the pre-existing invalid package fingerprint
  0xdeadbeef. Zig's suggested replacement fingerprint varies with the source
  state. The package manifest was left untouched because this is a lint-only PR.
• Zig 0.15.1 zig fmt --check build.zig: passes. Before changes,
  zig fmt --check . flagged build.zig.
• Remaining warning: gdzig-public-docs for the template's public build
  entrypoint. Left in place rather than adding boilerplate documentation to the
  minimal example solely to silence a warning.

Notes

• --deny-warnings is intentionally not enabled while the public-docs warning
  remains.