fix: close-account missed discriminator in space calc

`basics/close-account/anchor` had `space = UserState::INIT_SPACE` in the `CreateUserContext` init constraint. Anchor does NOT auto-add the 8-byte account discriminator — `space` is passed literally to `system_program::create_account`. The correct form is always:

    space = Struct::DISCRIMINATOR.len() + Struct::INIT_SPACE

UserState layout:
  8  discriminator (required on every Anchor account, written before the struct body)
  1  bump: u8
 32  user: Pubkey
  4  String length prefix
 50  max_len name bytes
 ---
 95  total bytes needed
 87  INIT_SPACE (just the struct body, NO discriminator)

The old code allocated 87 bytes. On create, Anchor's `try_serialize` writes 8 discriminator bytes then up to 87 bytes of struct body using a `BpfWriter` over the account's data slice. With only 87 bytes of slice, that's 95 bytes into 87 bytes = short-write → `AccountDidNotSerialize`.

Why the existing test (`test_close_account.rs`) doesn't catch this: the test creates a user with name "John Doe" — 8 bytes of actual string plus the 4-byte length prefix = 12 bytes for the `name` field instead of the 54 bytes a max-length name would need. That gives an actual serialized size of 8 + 1 + 32 + 4 + 8 = 53 bytes, well under the 87-byte allocation. The bug only fires for names longer than 42 UTF-8 bytes — under the 50-byte advertised max.

Real bug. Fix verified with `cargo check --workspace`.

5th of 5 commits in the skill-audit cleanup.

Author: mikemaccana-edwardbot

basics/close-account/anchor/programs/close-account/src/instructions/create_user.rs

@@ -9,7 +9,7 @@ pub struct CreateUserContext<'info> {
     #[account(
         init,
         payer = user,
-        space = UserState::INIT_SPACE,
+        space = UserState::DISCRIMINATOR.len() + UserState::INIT_SPACE,
         seeds = [
             b"USER",
             user.key().as_ref(),