fix: validate Lighter API key hex format before WASM signer

Go WASM hex decoder gives cryptic errors on invalid keys (e.g. dots).
Now checks for valid hex chars first, logs clear message with fix
command, and falls back to read-only mode instead of crashing.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Hiksang

src/exchanges/lighter.ts

@@ -126,15 +126,22 @@ export class LighterAdapter implements ExchangeAdapter {
 
     // Initialize signer for trading if we have an API key (reuse singleton WASM client)
     if (this._apiKey && !signerReady) {
-      const client = await LighterAdapter.getWasmClient();
-      await client.createClient({
-        url: this._baseUrl,
-        privateKey: this._apiKey,
-        chainId: this._chainId,
-        apiKeyIndex: this._apiKeyIndex,
-        accountIndex: this._accountIndex,
-      });
-      this._signer = client;
+      // Validate API key is valid hex before passing to WASM (Go hex decoder gives cryptic errors otherwise)
+      const stripped = this._apiKey.startsWith("0x") ? this._apiKey.slice(2) : this._apiKey;
+      if (!/^[0-9a-fA-F]+$/.test(stripped)) {
+        console.error(`[lighter] Invalid API key format (expected hex, got non-hex chars). Run 'perp -e lighter manage setup-api-key' to regenerate.`);
+        this._apiKey = "";
+      } else {
+        const client = await LighterAdapter.getWasmClient();
+        await client.createClient({
+          url: this._baseUrl,
+          privateKey: this._apiKey,
+          chainId: this._chainId,
+          apiKeyIndex: this._apiKeyIndex,
+          accountIndex: this._accountIndex,
+        });
+        this._signer = client;
+      }
     }
     if (this._apiKey) {
       this._readOnly = false;