deps: bump zspec v0.9.1 → v0.9.2 — fixes Linux CI deadlock

zspec v0.9.1's `.simple`-mode runner left `std.testing.io_instance`
uninitialized; any test reaching for `std.testing.io` blocks forever
on Linux on a zero-init `Io.Threaded` pool. zspec#44 (closed) fixed
it in v0.9.2. Latent in this repo until a tmpDir-using test gets
added; bumping proactively per the toolkit-wide audit.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: apotema

build.zig.zon

@@ -6,8 +6,8 @@
 
     .dependencies = .{
         .zspec = .{
-            .url = "https://github.com/apotema/zspec/archive/v0.9.1.tar.gz",
-            .hash = "zspec-0.9.1-jaKLbbX4AwBKANdetxzzWc3UTO0UY0lcJJzTagQHlt5K",
+            .url = "https://github.com/apotema/zspec/archive/v0.9.2.tar.gz",
+            .hash = "zspec-0.9.1-jaKLbXgMBACFwbNjflhbMyP113leoYjboxn-1UOP-FGw",
         },
     },