feat(cli): surface a notice when output sanitization strips metadata

Give operators/agents visibility into when the CLI neutralizes suspicious token
metadata in an API response.

- sanitizeForOutputWithCount returns the cleaned value plus the number of altered
  strings; sanitizeForOutput kept as a thin wrapper
- printResult prints "[gmgn-cli] Notice: neutralized N suspicious metadata value(s)"
  to stderr when anything was filtered (extra detail under GMGN_DEBUG); sanitized
  JSON still goes to stdout so piping is unaffected
- document the notice in the gmgn-token SKILL untrusted-data warning

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/output.ts

@@ -1,10 +1,22 @@
-import { sanitizeForOutput } from "./sanitize.js";
+import { sanitizeForOutputWithCount } from "./sanitize.js";
 
 export function printResult(data: unknown, raw?: boolean): void {
   // Neutralize any attacker-controlled metadata (token name/symbol/description/
   // social links, on-chain URIs, etc.) before it is emitted and read by an AI
   // agent. Defends against indirect prompt injection via token metadata.
-  const safe = sanitizeForOutput(data);
+  const { data: safe, changed } = sanitizeForOutputWithCount(data);
+  if (changed > 0) {
+    // Surface that filtering occurred so a human/agent knows the response
+    // contained suspicious metadata. Extra detail is gated behind GMGN_DEBUG.
+    console.error(
+      `[gmgn-cli] Notice: neutralized ${changed} suspicious metadata value(s) in this response (possible prompt-injection attempt).`
+    );
+    if (process.env.GMGN_DEBUG) {
+      console.error(
+        `[gmgn-cli] sanitized ${changed} field(s); replaced injection framing with "[filtered]" and removed hidden characters.`
+      );
+    }
+  }
   if (raw) {
     console.log(JSON.stringify(safe));
   } else {