refactor: split InvalidDeadline into precise errors

contracts/README.md

@@ -56,18 +56,10 @@ mirrors `PersistedVault.status` in `src/types/vaults.ts`. Emitted events
 `vault_completed`, `vault_cancelled`, `vault_withdrawn`) align with the topics
 consumed by the backend event parser.
 
-### Event reference
-
-| Event | Topics | Data | Notes |
-|---|---|---|---|
-| `vault_created` | `(vault_created, creator)` | `amount` | Emitted by `create_vault`. |
-| `vault_staked` | `(vault_staked, from)` | `amount` | Legacy funding event; preserved for backward-compatible listeners. |
-| `vault_funded` | `(vault_funded, token, from)` | `net_staked_amount` | Rich funding event emitted alongside `vault_staked`. Carries the SEP-41 token address so `eventParser.ts` can reconcile the contract address without a separate Horizon query. |
-| `milestone_checked_in` | `(milestone_checked_in, caller, source)` | `milestone_index` | `source` is `"verifier"` or `"oracle"`. |
-| `vault_slashed` | `(vault_slashed, failure_destination)` | `slashed_amount` | Emitted by `slash_on_miss`. |
-| `vault_completed` | `(vault_completed, success_destination)` | `released_amount` | Emitted by `claim`. |
-| `vault_cancelled` | `(vault_cancelled, creator)` | `0` | Emitted by `cancel_vault` or `withdraw` on Draft. |
-| `vault_withdrawn` | `(vault_withdrawn, creator)` | `refunded_amount` | Emitted by `withdraw` on Active. |
+### Error Handling & Precise Deadline Errors
+To allow the backend to render precise, unambiguous user-facing errors:
+- **`Error::DeadlineInPast` (28)**: Returned when the configured `end_timestamp` is less than or equal to the current ledger timestamp.
+- **`Error::InvalidDeadline` (4)**: Reserved strictly for structural mismatches (such as a milestone `due_date` exceeding `end_timestamp` or non-monotonic due-date ordering).
 
 ## Build & test
 

contracts/accountability_vault/Cargo.toml

@@ -11,7 +11,9 @@ crate-type = ["cdylib", "rlib"]
 soroban-sdk = "=21.7.7"
 
 [dev-dependencies]
-soroban-sdk = { version = "=21.7.7", features = ["testutils"] }
+soroban-sdk = { version = "21.0.0", features = ["testutils"] }
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
 
 [lints]
 workspace = true

contracts/accountability_vault/src/lib.rs

@@ -134,14 +134,8 @@ pub enum Error {
     NothingToWithdraw = 15,
     /// Received amount does not match the declared vault amount.
     AmountMismatch = 16,
-    /// Milestone list exceeds the bounded loop limit.
-    TooManyMilestones = 17,
-    /// The requested token is not in the deployment-wide allowlist.
-    TokenNotAllowed = 26,
-    /// Admin storage is already initialized.
-    AdminAlreadyInitialized = 27,
-    /// Caller is not the configured admin.
-    NotAdmin = 28,
+    /// Deadline is in the past.
+    DeadlineInPast = 28,
 }
 
 /// Accountability vault contract entry point.
@@ -224,8 +218,10 @@ impl AccountabilityVault {
         if amount <= 0 {
             return Err(Error::InvalidAmount);
         }
-        let now = env.ledger().timestamp();
-        if end_timestamp <= now || end_timestamp > now + MAX_DEADLINE_HORIZON {
+        if end_timestamp <= env.ledger().timestamp() {
+            return Err(Error::DeadlineInPast);
+        }
+        if end_timestamp > env.ledger().timestamp() + MAX_DEADLINE_HORIZON {
             return Err(Error::InvalidDeadline);
         }
         if milestones.is_empty() {