fix: remove seconds-precision time from env context to stop breaking token cache

Current time with HH:MM:SS changed every second, invalidating the prompt cache
on every request. Date-level precision is sufficient; timezone and locale are
stable. Removes Current time field entirely from createEnvContext output.

src/agents/env-context.ts

@@ -1,5 +1,5 @@
 /**
- * Creates OmO-specific environment context (time, timezone, locale).
+ * Creates OmO-specific environment context (timezone, locale).
  * Note: Working directory, platform, and date are already provided by OpenCode's system.ts,
  * so we only include fields that OpenCode doesn't provide to avoid duplication.
  * See: https://github.com/code-yeongyu/oh-my-opencode/issues/379
@@ -16,17 +16,9 @@ export function createEnvContext(): string {
     day: "numeric",
   })
 
-  const timeStr = now.toLocaleTimeString(locale, {
-    hour: "2-digit",
-    minute: "2-digit",
-    second: "2-digit",
-    hour12: true,
-  })
-
   return `
 <omo-env>
   Current date: ${dateStr}
-  Current time: ${timeStr}
   Timezone: ${timezone}
   Locale: ${locale}
 </omo-env>`