[CathyZaks]

[contract] Use one assets base for share pricing and reconcile conversion tests

Problem

Share conversions (share_price, calculate_shares, calculate_assets, deposit, gasless_deposit, withdraw, execute_withdrawal) were reading only idle state.total_assets rather than total_assets(), which includes strategy valuation. As a result:

• Deposits into a vault after funds were partially deployed to a strategy minted shares at an incorrect, artificially deflated asset base, diluting prior depositors.
• Share price reporting ignored strategy holdings.
• In vault/src/test.rs, expectations after divest(10) assumed an incorrect asset base.
• In share-price-math/src/fuzz_invariants.rs, the validity filter prematurely returned on total_assets == 0 && total_shares > 0, skipping the zero-idle state where idle assets are zero while shares remain outstanding.

Solution

• Consolidated share pricing and conversions to use total_assets() (idle assets plus strategy value) as the canonical asset base across all conversion and deposit/withdrawal functions.
• Reconciled test_vault_with_benji_strategy withdrawal math to reflect proportional share of total_assets().
• Added test verifying deposits mint at the correct price when a strategy holds part of the assets.
• Narrowed is_valid_vault_state in fuzz_invariants.rs to allow non-negative assets with positive shares so the zero-idle state is exercised.

Changes

• contracts/vault/src/lib.rs:
  • share_price: Uses total_assets(env).unwrap_or(state.total_assets) instead of state.total_assets.
  • calculate_shares & calculate_assets: Reads total_assets(env)? and converts against total vault assets.
  • deposit & gasless_deposit: Reads total_assets(env)? for TVL risk limits, try_assets_to_shares, and effective asset computation for dust sweeping.
  • withdraw & execute_withdrawal: Uses total_assets(env)? to determine assets_to_return.
• contracts/vault/src/test.rs:
  • Reconciled test_vault_with_benji_strategy expectations where 50 shares withdraw 53 assets out of 106 total assets.
  • Added test_deposit_mints_at_correct_price_while_strategy_holds_part_of_assets.
• contracts/share-price-math/src/fuzz_invariants.rs:
  • Narrowed is_valid_vault_state condition to (total_shares == 0 && total_assets == 0) || (total_shares > 0 && total_assets >= 0).
  • Added unit test zero_idle_state_invariant_holds.

Testing

• Ran unit tests for share-price-math (cargo test -p share-price-math), passing all 15 tests including the new zero-idle invariant test.

Closes #1632