[timiturn3r]

#closes #15
Description
Fixes a critical vulnerability in the claims-processor contract where auto_process lacked an initial idempotency guard.

Previously, if a keeper triggered auto_process multiple times simultaneously or sequentially for the same policy, the contract would skip internal state checks and repeatedly execute the evaluation pipeline. If downstream guards in the Policy Engine were ever altered or bypassed, this would result in duplicate claim entries, multiple cross-contract calls, and potential double-payouts/escrow draining.

This PR introduces a defensive persistent storage lookup at the absolute top of the auto_process pipeline, tracking the state natively within the claims-processor workspace.

Fix Details
claims-processor/src/types.rs: Added the AlreadyProcessed variant to the ClaimResult enum.

claims-processor/src/lib.rs:

Injected a strict persistent storage guard checking StorageKey::PolicyClaim(policy_id) at the entry point of auto_process.

Early-returns ClaimResult::AlreadyProcessed if an active or settled claim record already exists for the given policy ID.

claims-processor/src/test_integration.rs: Brought the soroban_sdk::testutils::Ledger trait into scope to resolve cross-contract time-warping compilation issues (.with_mut()).

claims-processor/src/test.rs: Updated test_double_process_idempotent to assert the newly expected, explicit AlreadyProcessed result instead of downstream result codes.

Related Issues
Closes #15

Testing Checklist
[x] Verified via local unit and integration tests.

[x] Compilation warnings cleared (unused variables handled).

Bash

Output from localized verification run:

running 11 tests
test test::test_expired_policy_no_payout ... ok
test test::test_good_rainfall_no_payout ... ok
test test::test_double_process_idempotent ... ok
test test::test_double_submit_claim_panics - should panic ... ok
test test::test_non_policyholder_cannot_submit_claim - should panic ... ok
test test::test_drought_trigger_pays_out ... ok
test test_integration::batch_processes_multiple_pending_claims ... ok
test test::test_manual_claim_flow ... ok
test test_integration::batch_skips_non_pending_claims ... ok
test test_integration::test_stale_oracle_data_rejected - should panic ... ok
test test_integration::test_fresh_oracle_data_accepted ... ok

test result: ok. 11 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.51s
Storage & Security Considerations
Uses the persistent storage tier to prevent expiration of claim records, ensuring the idempotency guard remains durable over long operational timelines.

Adheres to Soroban contract-isolation best practices by making the contract responsible for validation of its own internal process state.
#closes

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