feat(ENG-263): CreateAccount CPI with pointer walk and relative offset macro

[alnoki]

Changes

1. Implement CreateAccount CPI in register.s, populating
   CreateAccountData (space, lamports, owner), SolAccountInfo
   and SolAccountMeta fields, SolSignerSeeds, SolInstruction,
   and invoking sol_invoke_signed_c
2. Add relative_offset! constant form to constant_group! that
   computes the difference between two field offsets within the same
   struct, emitted as an i32 immediate with _REL_OFF_IMM suffix
   (works in both frame and non-frame contexts)
3. Add CPI pointer walk in assembly that chains add64 through
   input buffer account fields (address, owner, lamports, data) and
   across accounts using relative_offset! constants, eliminating
   redundant mov64 r10 loads
4. Simplify signer_seeds! and cpi_accounts! macro syntax by
   removing the pub struct requirement (always emitted implicitly)
5. Add primitive type support to size_of_group! (e.g. u8) by
   skipping the super:: prefix for prelude types
6. Add CPI constant group with WRITABLE_SIGNER mask (0x0101)
   for half-word stores that set both is_signer and is_writable
7. Add ACCT_DATA_OFF, ACCT_STORAGE_OVERHEAD, IB_USER_PUBKEY,
   and SIZE_OF_* constants for u8, MarketHeader, and
   CreateAccountData
8. Add SolSignerSeeds field to Frame, rename struct from
   RegisterMarketFrame to Frame and module from
   register_market_frame to frame
9. Add CreateAccountHappyPath integration test verifying account
   owner, data length, and rent exemption after CPI execution
10. Set Mollusk exemption_threshold = 1.0 (SIMD-0194) in test
    setup (pending fix: remove rent exemption threshold multiplier anza-xyz/mollusk#219)
11. Update REGISTER-MARKET pseudocode with full CPI flow and
    remove math-mode wrapping from variable references in both
    .tex algorithm files
12. Document relative_offset! in build-scaffolding docs

[linear]

ENG-263