fix: prevent false positive context overflow detection in conversation text

The isContextOverflowError check was too broad - it matched any text containing
'context overflow', including legitimate conversation discussing the topic.

Changed to require 'context overflow:' (with colon) to only match actual error
messages like 'Context overflow: Summarization failed'.

Added test case to verify normal conversation text doesn't trigger false positives.

src/agents/pi-embedded-helpers.iscontextoverflowerror.test.ts

@@ -46,4 +46,12 @@ describe("isContextOverflowError", () => {
     expect(isContextOverflowError("model not found")).toBe(false);
     expect(isContextOverflowError("authentication failed")).toBe(false);
   });
+
+  it("ignores normal conversation text mentioning context overflow", () => {
+    // These are legitimate conversation snippets, not error messages
+    expect(isContextOverflowError("Let's investigate the context overflow bug")).toBe(false);
+    expect(isContextOverflowError("The mystery context overflow errors are strange")).toBe(false);
+    expect(isContextOverflowError("We're debugging context overflow issues")).toBe(false);
+    expect(isContextOverflowError("Something is causing context overflow messages")).toBe(false);
+  });
 });

src/agents/pi-embedded-helpers/errors.ts

@@ -20,7 +20,7 @@ export function isContextOverflowError(errorMessage?: string): boolean {
     lower.includes("prompt is too long") ||
     lower.includes("exceeds model context window") ||
     (hasRequestSizeExceeds && hasContextWindow) ||
-    lower.includes("context overflow") ||
+    lower.includes("context overflow:") ||
     (lower.includes("413") && lower.includes("too large"))
   );
 }