fix(vault): align simulate_deduct with deduct via shared validate_deduct

[Manta-Byte]

Closes #1115

Summary

simulate_deduct claimed parity with deduct but checked different things. Both now call one shared validate_deduct, so the preflight returns the same error the live call would for caller, pause state, amount bounds and balance.

Criteria → code and tests

Criterion	Code	Test
Simulator and deduct share one validation function	validate_deduct in lib.rs, called by deduct and by simulate_deduct in views.rs	parity proptest
Below-min amounts rejected by both with BelowMinDeposit	require_valid_deduct_amount inside validate_deduct	explicit simulate / try_deduct BelowMinDeposit test
Parity proptest compares simulate vs try_deduct error codes over 256 cases	n/a	test_simulate_parity.rs: random amount, caller, paused flag and balance; ProptestConfig::with_cases(256); asserts identical error codes or both succeed
Module docs describe the actual parameter list	views.rs module docs rewritten	n/a

Behavior changes

• simulate_deduct signature is now (env, caller, amount, request_id: u64). It previously took Option<Symbol> plus max_fee_bps and developer.
• Slippage removed from the simulator. deduct never implemented it, so the simulator produced false failures. Implementing it in deduct would change on-chain behavior, so I removed it from the simulator instead. Happy to go the other way if you prefer.
• The simulator no longer checks duplicate request ids or rate limits, since deduct doesn't either.
• The simulator now performs the authorized-caller check it was missing.
• docs/interfaces/vault.json updated to the new simulate_deduct signature.

Design and failure modes

• validate_deduct is read-only: no storage writes, no events, no auth. Check order and error values for deduct are unchanged (authorized caller, pause, amount bounds, balance).
• validate_deduct takes (env, caller, amount). request_id is not validated by deduct, so it isn't passed in. simulate_deduct keeps the parameter for interface alignment.
• caller.require_auth() stays in deduct only, so the simulator can be called without auth and never panics on it.
• The shared validator covers caller, pause, amount bounds and balance. Checks deduct performs around token transfer (settlement / USDC configuration), if any, are outside it.

Compatibility

simulate_deduct is a view, so there are no storage or state changes and existing deployments are unaffected. Callers of the old signature must update; I found none in this repo outside the vault crate (older status reports in the repo root describe a previous signature and were left untouched). proptest is added as a dev-dependency only, using the same feature set as callora-settlement.

Validation

cargo test -p callora-vault simulate

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