totalSupplyBootstrapped is derivable from totalSupplyLatestSplit

[thedavidmeister]

CorporateActionStorage.totalSupplyBootstrapped is a bool that tracks whether LibTotalSupply.fold() has performed the one-time bootstrap (copying OZ's _totalSupply into unmigrated[0]). It guards onMint / onBurn from writing to the pot pre-bootstrap and drives effectiveTotalSupply's fallback-to-OZ branch.

The bool is derivable from totalSupplyLatestSplit:

• Pre-bootstrap: bootstrapped = false, totalSupplyLatestSplit = 0 (no split tracked yet).
• Post-bootstrap: bootstrapped = true, totalSupplyLatestSplit > 0 (the walk inside fold() always advances past the triggering first-completed-split before returning).

At every _update boundary, totalSupplyBootstrapped <=> (totalSupplyLatestSplit != 0). The bool adds no information the uint256 doesn't already encode.

Costs:

• One struct slot dedicated to holding a 1-byte bool. Any future struct field change has to account for its position.
• One one-time SSTORE (20k gas) on first bootstrap.
• Three SLOAD sites (onMint, onBurn, effectiveTotalSupply) that could read totalSupplyLatestSplit instead.

Related: proper sentinels

This is a specific instance of the broader pattern in #79: the corporate-actions storage relies on positional / convention-based disambiguation (0-means-unset) rather than value-level sentinels. If #79 is adopted and type(uint256).max becomes the "not set" value for pointer-like fields, totalSupplyLatestSplit would carry the same "bootstrap fired?" signal unambiguously with no separate bool.

Options

1. Drop the bool, replace every if (bootstrapped) with if (totalSupplyLatestSplit != 0). Zero storage footprint, same semantics.
2. Adopt proper sentinels per Linked list uses positional disambiguation instead of value-level disambiguation for null pointers #79, then item 1 falls out naturally.

No runtime behaviour change in either option.

[thedavidmeister]

Resolved by #124 — totalSupplyBootstrapped is dropped from CorporateActionStorage; the s.nodes.length != 0 test replaces every callsite. PR #124 derives bootstrapped-ness from list state directly, eliminating the redundant flag.