fix(ci): gitignore vite/vitest *.timestamp-*.mjs to stop turbo traversal race

The push/ci lint step intermittently failed with:

  x Package traversal error: .../packages/macp/vitest.config.ts.timestamp-
    <n>.mjs: IO error ... No such file or directory (os error 2)

vite/vitest/esbuild write a transient *.timestamp-*.mjs next to a TS
config while loading it, then unlink it. The files were untracked but not
ignored, so turbo's package traversal hashed them and raced the unlink.
Ignoring them excludes them from turbo's input set and removes the race.

Same class of fix as the pglite timeout/OOM change in this PR: transient
test tooling artifacts destabilising CI.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -15,3 +15,10 @@ infra/step-ca/dev-password
 
 # Scratch dirs created by the framework git-wrapper shell test harnesses
 .mosaic-test-work/
+
+# Transient config files vite/vitest/esbuild write next to a *.config.ts while
+# loading it, then unlink. They are untracked but were not ignored, so turbo's
+# package traversal hashed them and intermittently failed CI with "Package
+# traversal error: ... .timestamp-*.mjs: No such file or directory" when the
+# file vanished mid-scan. Ignoring them removes the race.
+*.timestamp-*.mjs