chore(vendor): import pi 0.85.1

Imported as a linear vendor commit so forge rebases do not replay the upstream root tree.

git-subtree-dir: third_party/pi

git-subtree-split: d981de1229ef899957bbe968bc8dcda02a21f477

third_party/pi/packages/ai/src/api/openai-prompt-cache.ts

@@ -0,0 +1,8 @@
+export const OPENAI_PROMPT_CACHE_KEY_MAX_LENGTH = 64;
+
+export function clampOpenAIPromptCacheKey(key: string | undefined): string | undefined {
+	if (key === undefined) return undefined;
+	const chars = Array.from(key);
+	if (chars.length <= OPENAI_PROMPT_CACHE_KEY_MAX_LENGTH) return key;
+	return chars.slice(0, OPENAI_PROMPT_CACHE_KEY_MAX_LENGTH).join("");
+}