Fix release CI: upgrade mlugg/setup-zig to v2 and cut 0.0.3

`mlugg/setup-zig@v1` is deprecated and only knows the pre-0.14
tarball name (`zig-linux-x86_64-<ver>.tar.xz`), so every mirror —
and the official ziglang.org/builds — returned 404 for Zig 0.15.2
on both the v0.0.1 and v0.0.2 release runs. v2 uses the new
`zig-x86_64-linux-<ver>.tar.xz` layout that Zig switched to in
0.14+.

Also rolls the existing CHANGELOG `[Unreleased]` work into a
dated `[0.0.3]` section and adds the CI fix to its Fixed list.

CHANGELOG.md

@@ -6,6 +6,8 @@ loosely follows [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+## [0.0.3] - 2026-05-15
+
 ### Added
 - Auto-summarization for top-level agent tabs. patterm now loads
   `$XDG_CONFIG_HOME/patterm/settings.json`, enables Codex-based
@@ -68,6 +70,13 @@ loosely follows [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
   the command field.
 
 ### Fixed
+- Release workflow (`.gitea/workflows/release.yml`) now uses
+  `mlugg/setup-zig@v2` instead of the deprecated `@v1`. v1 hard-coded
+  the pre-0.14 tarball name (`zig-linux-x86_64-<ver>.tar.xz`), so
+  every mirror and the official `ziglang.org/builds` returned 404 for
+  Zig 0.15.2 and the v0.0.1 / v0.0.2 tag pushes never produced a
+  release asset. v2 uses the post-0.14 `zig-x86_64-linux-<ver>.tar.xz`
+  layout, so the runner can fetch Zig and build patterm.
 - Typing into a focused child while its emulator viewport is
   scrolled up into scrollback history now auto-snaps the viewport
   back to the live area. Previously the keystroke reached the