Fix: prevent system-reminder tags from triggering mode keywords (#1155)

Automated system messages with <system-reminder> tags were incorrectly
triggering [search-mode], [analyze-mode], and other keyword modes when
they contained words like "search", "find", "explore", etc.

Changes:
- Add removeSystemReminders() to strip <system-reminder> content before keyword detection
- Add hasSystemReminder() utility function
- Update keyword-detector to clean text before pattern matching
- Add comprehensive test coverage for system-reminder filtering

Fixes issue where automated system notifications caused agents to
incorrectly enter MAXIMUM SEARCH EFFORT mode.

Co-authored-by: TheEpTic <git@eptic.me>

src/shared/system-directive.ts

@@ -26,6 +26,26 @@ export function isSystemDirective(text: string): boolean {
   return text.trimStart().startsWith(SYSTEM_DIRECTIVE_PREFIX)
 }
 
+/**
+ * Checks if a message contains system-generated content that should be excluded
+ * from keyword detection and mode triggering.
+ * @param text - The message text to check
+ * @returns true if the message contains system-reminder tags
+ */
+export function hasSystemReminder(text: string): boolean {
+  return /<system-reminder>[\s\S]*?<\/system-reminder>/i.test(text)
+}
+
+/**
+ * Removes system-reminder tag content from text.
+ * This prevents automated system messages from triggering mode keywords.
+ * @param text - The message text to clean
+ * @returns text with system-reminder content removed
+ */
+export function removeSystemReminders(text: string): string {
+  return text.replace(/<system-reminder>[\s\S]*?<\/system-reminder>/gi, "").trim()
+}
+
 export const SystemDirectiveTypes = {
   TODO_CONTINUATION: "TODO CONTINUATION",
   RALPH_LOOP: "RALPH LOOP",