fix(agents): make tool call ID sanitization conditional with standard/strict modes

- Add ToolCallIdMode type ('standard' | 'strict') for provider compatibility
- Standard mode (default): allows [a-zA-Z0-9_-] for readable session logs
- Strict mode: only [a-zA-Z0-9] for Mistral via OpenRouter
- Update sanitizeSessionMessagesImages to accept toolCallIdMode option
- Export ToolCallIdMode from pi-embedded-helpers barrel

Addresses review feedback on PR #1372 about readability.

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

@@ -1,5 +1,6 @@
 import type { AgentMessage, AgentToolResult } from "@mariozechner/pi-agent-core";
 
+import type { ToolCallIdMode } from "../tool-call-id.js";
 import { sanitizeToolCallIdsForCloudCodeAssist } from "../tool-call-id.js";
 import { sanitizeContentBlocksImages } from "../tool-images.js";
 import { stripThoughtSignatures } from "./bootstrap.js";
@@ -32,6 +33,8 @@ export async function sanitizeSessionMessagesImages(
   label: string,
   options?: {
     sanitizeToolCallIds?: boolean;
+    /** Mode for tool call ID sanitization: "standard" (default, preserves _-) or "strict" (alphanumeric only) */
+    toolCallIdMode?: ToolCallIdMode;
     enforceToolCallLast?: boolean;
     preserveSignatures?: boolean;
     sanitizeThoughtSignatures?: {
@@ -43,7 +46,7 @@ export async function sanitizeSessionMessagesImages(
   // We sanitize historical session messages because Anthropic can reject a request
   // if the transcript contains oversized base64 images (see MAX_IMAGE_DIMENSION_PX).
   const sanitizedIds = options?.sanitizeToolCallIds
-    ? sanitizeToolCallIdsForCloudCodeAssist(messages)
+    ? sanitizeToolCallIdsForCloudCodeAssist(messages, options.toolCallIdMode)
     : messages;
   const out: AgentMessage[] = [];
   for (const msg of sanitizedIds) {