release: v0.5.0

Promote the Zig 0.16.0 migration's `Unreleased` CHANGELOG section to
`v0.5.0 (2026-04-27)` and bump `build.zig.zon` `version` from the stale
"0.3.0" placeholder to "0.5.0" (matching the existing tag sequence —
v0.4.0 was the last release).

Migration highlights (full list in CHANGELOG):
- Zig 0.15.2 → 0.16.0
- zwasm v1.9.1 → v1.11.0
- New `runtime/io_default.zig` for the std.Io reshape
- Binary 4.12 MB / startup 4.1 ms / RSS 8.2 MB
- 1324/1324 unit tests + 83 cljw test namespaces + 6 wasm e2e all green
- Four features (HTTP server/client, nREPL, raw line editor,
  `cljw build`) temporarily stubbed; tracked as F140-F144.

Author: chaploud

CHANGELOG.md

@@ -1,6 +1,6 @@
 # Changelog
 
-## Unreleased
+## v0.5.0 (2026-04-27)
 
 ### Toolchain
 - Migrate from Zig 0.15.2 to Zig 0.16.0 (D111). All `std.Io` reshapes

build.zig.zon

@@ -1,6 +1,6 @@
 .{
     .name = .clojure_wasm,
-    .version = "0.3.0",
+    .version = "0.5.0",
     .dependencies = .{
         .zwasm = .{
             .url = "https://github.com/clojurewasm/zwasm/archive/v1.11.0.tar.gz",