Fix metadata MetadataPointerInstruction encoding: use PodCOption (4-byte flags)

The MetadataPointerInstruction::Initialize uses PodCOption<Pubkey> which
encodes with a 4-byte LE flag ([1,0,0,0] for Some) + 32-byte pubkey,
making each field 36 bytes. Total instruction: 74 bytes.

Previous attempts used 1-byte COption flags (66 and 68 bytes), which
caused InvalidInstructionData because the validator requires exactly
[1,0,0,0] or [0,0,0,0] for the 4-byte option field.

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

Author: mikemaccana

tokens/token-2022/metadata/quasar/src/lib.rs

@@ -99,14 +99,17 @@ pub fn handle_initialize(
         .invoke()?;
 
     // InitializeMetadataPointer: opcode 39, sub-opcode 0.
-    // Layout: [39, 0, COption_flag(1), authority(32), COption_flag(1), metadata_address(32)]
-    let mut mp_data = [0u8; 68];
+    // Uses PodCOption<Pubkey> encoding: 4-byte LE flag + 32-byte pubkey = 36 bytes each.
+    // Layout: [39, 0, 1,0,0,0, authority(32), 1,0,0,0, metadata_address(32)] = 74 bytes
+    let mut mp_data = [0u8; 74];
     mp_data[0] = 39;
     mp_data[1] = 0;
-    mp_data[2] = 1; // COption::Some for authority
-    mp_data[3..35].copy_from_slice(accounts.payer.to_account_view().address().as_ref());
-    mp_data[35] = 1; // COption::Some for metadata_address
-    mp_data[36..68]
+    mp_data[2] = 1; // PodCOption::Some flag (4-byte LE: [1,0,0,0])
+    // mp_data[3..6] already zero
+    mp_data[6..38].copy_from_slice(accounts.payer.to_account_view().address().as_ref());
+    mp_data[38] = 1; // PodCOption::Some flag (4-byte LE: [1,0,0,0])
+    // mp_data[39..42] already zero
+    mp_data[42..74]
         .copy_from_slice(accounts.mint_account.to_account_view().address().as_ref());
 
     CpiCall::new(