Add Quasar port of the order-book (CLOB) example

[mikemaccana]

Ports finance/order-book/anchor to Quasar under finance/order-book/quasar, alongside the existing Quasar examples. Both builds share the same program ID (C69UJ8irfmHq5ysyLek7FKApHR86FBeupiz4JnoyPzzx), so clients and PDA derivations work against either unchanged.

What's preserved

The trading logic, fee model, two-lot pricing, and the OpenBook-derived critbit matching engine are faithful to the Anchor build. A side-by-side review confirmed the fee/lock/rebate/cancel arithmetic and the Bid/Ask fill-credit branches are identical.

Quasar-specific adaptations

Quasar is zero-copy, no_std, and zero-allocation, so a few things differ by necessity:

• Order book (~180 KB, two zero-copy slabs) is accessed by casting the raw account bytes with bytemuck — Quasar has no AccountLoader. An 8-byte discriminator guards the cast, and the client pre-creates the account (too large for an init CPI, which is capped at 10 KB).
• MarketUser.open_orders is a fixed [u8; 160] (20 packed u64s) + length instead of a borsh Vec<u64>, keeping the account fixed-size so maker accounts (passed as remaining accounts) mutate in place.
• The slab is heap-free: fixed-array traversal stack (critbit depth ≤ 128), two write-only upstream stacks removed, and place_order crosses at most MAX_FILLS (16) orders per call.
• side / order status / order side stored as u8 (zero-copy POD); place_order takes side: u8 and an order_id verified against the book's next_order_id.

Tests & docs

• QuasarSVM integration tests in src/tests.rs drive the full lifecycle — initialize a market, create users, rest an ask, cross it with a bid, settle both sides, withdraw the fee — asserting on-chain state, token balances, and fee accounting, plus an authorization rejection.
• README documents the accounts/PDAs, the two-lot model, the instruction lifecycle, the matching engine, and every Quasar-specific adaptation.

Validation

Verified with the host toolchain: cargo build and cargo clippy --all-targets are clean (only the framework's idl-build cfg warnings, same as the existing finance/escrow/quasar), and cargo test --no-run compiles and links the QuasarSVM suite. The SBF build + test run happens in the Quasar CI (quasar build then cargo test); it couldn't run in the authoring sandbox because Solana platform-tools weren't reachable there.

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https://claude.ai/code/session_016ATxCcgrZxaL5dMZSyWj1K

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