refactor: contract size cuts

[BenSparksCode]

Changes (detailed changes in each sub-PR below):

• refactor: split most of Factory out to FactoryLib #443
• chore: bump to Solidity 0.8.28 for transient keyword #442

Size Diffs

Contract	Before	After	Diff
Atlas.sol	25,526	24,188	-1,338

The net effect on contract size is that Atlas.sol is 388 bytes under the limit, which should be enough room for the additional logic needed in the Arbitrum version.

Gas Diffs

Test	Before	After	Diff
Atlas Swap Intent with Basic RFQ	382,733	384,088	+1,355
Ex Post Ordering	1,287,743	1,289,789	+2,046
Chainlink OEV Standard Version	434,115	436,573	+2,458
Treble Swap Metacall ERC20 to ERC20 with One Solver	677,597	681,346	+3,749
Treble Swap Metacall ETH to ERC20 with One Solver	543,766	546,031	+2,265

Gas costs increased slightly (~0.5%), mostly due to the delegatecall overhead needed any time a Factory.sol function is called.