Fix: Use deterministic date format in classifier prompt

toLocaleString() produces different output between Node and Bun:
- Node: "Jan 1, 2000, 1:00 PM"
- Bun: "Jan 1, 2000 at 1:00 PM"

This caused different prompt signatures between local (Bun) and CI (Node),
breaking fixture cache lookups.

Also: Don't load .env in CI for vitest to ensure tests use fixture cache only.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: ndbroadbent

src/classifier/prompt.ts

@@ -123,16 +123,31 @@ function formatCandidateWithContext(
 
 /**
  * Format timestamp for display in prompt.
+ * Uses deterministic format to avoid locale differences between environments.
  */
 function formatTimestamp(date: Date): string {
-  return date.toLocaleString('en-US', {
-    month: 'short',
-    day: 'numeric',
-    year: 'numeric',
-    hour: 'numeric',
-    minute: '2-digit',
-    hour12: true
-  })
+  const months = [
+    'Jan',
+    'Feb',
+    'Mar',
+    'Apr',
+    'May',
+    'Jun',
+    'Jul',
+    'Aug',
+    'Sep',
+    'Oct',
+    'Nov',
+    'Dec'
+  ]
+  const month = months[date.getMonth()]
+  const day = date.getDate()
+  const year = date.getFullYear()
+  const hours = date.getHours()
+  const minutes = date.getMinutes().toString().padStart(2, '0')
+  const ampm = hours >= 12 ? 'PM' : 'AM'
+  const hour12 = hours % 12 || 12
+  return `${month} ${day}, ${year}, ${hour12}:${minutes} ${ampm}`
 }
 
 /**

vitest.config.ts

@@ -18,7 +18,8 @@ export default defineConfig(({ mode }) => ({
 		},
 	],
 	test: {
-		env: loadEnv(mode, process.cwd(), ""),
+		// Don't load .env in CI - tests must use fixture cache only
+		env: process.env.CI === "true" ? {} : loadEnv(mode, process.cwd(), ""),
 		globals: true,
 		include: ["src/**/*.test.ts", "tests/**/*.test.ts"],
 		exclude: ["src/cli/e2e/**/*.test.ts", "node_modules/**"],