fix(contracts): delegate purpose validation to CookieJarValidation library

CookieJar._validateWithdrawalConstraints had an inline bytes(purpose).length
check that duplicated and diverged from CookieJarValidation.validatePurpose.
Now delegates to the library which uses countUnicodeCodePoints, matching
client-side unicodeCodePointLength semantics for multi-byte characters.

Also replace remaining bun test references in README with bun run test.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Oba-One

README.md

@@ -116,11 +116,11 @@ cookie-jar/
 
 **Contracts**: Edit in `contracts/src/` → Auto-recompile → Auto-redeploy → Regen types  
 **Client**: `localhost:3000` with hot reload on Chain ID 31337  
-**Testing**: `bun test` (both contracts + client)
+**Testing**: `bun run test` (both contracts + client)
 
 ```bash
-bun test:contracts      # Smart contract tests
-bun test:client         # Frontend tests  
+bun run test:contracts  # Smart contract tests
+bun run test:client     # Frontend tests
 bun deploy:local        # Manual deployment
 bun seed:demo           # Refresh demo data
 ```
@@ -151,7 +151,7 @@ bun seed:demo           # Refresh demo data
 ```bash
 # Essential
 bun dev                    # Start local development
-bun test                   # Run all tests
+bun run test               # Run all tests
 bun build                  # Build contracts + client
 
 # Development variants  
@@ -479,7 +479,7 @@ Just clone, install, and develop!
 
 1. Fork the repository
 2. Create a feature branch: `git checkout -b feature/amazing-feature`
-3. Make your changes and test: `bun test`
+3. Make your changes and test: `bun run test`
 4. Commit with conventional commits: `git commit -m "feat: add amazing feature"`
 5. Push and create a Pull Request
 

contracts/src/CookieJar.sol

@@ -10,6 +10,7 @@ import {Pausable} from "@openzeppelin/contracts/utils/Pausable.sol";
 import {ReentrancyGuard} from "@openzeppelin/contracts/utils/ReentrancyGuard.sol";
 
 import {CookieJarLib} from "./libraries/CookieJarLib.sol";
+import {CookieJarValidation} from "./libraries/CookieJarValidation.sol";
 import {UniversalSwapAdapter} from "./libraries/UniversalSwapAdapter.sol";
 import {Streaming} from "./libraries/Streaming.sol";
 import {ISuperfluid, IConstantFlowAgreementV1} from "@superfluid-finance/ethereum-contracts/interfaces/superfluid/ISuperfluid.sol";
@@ -461,10 +462,8 @@ contract CookieJar is AccessControl, Pausable, ReentrancyGuard {
         if (amount == 0) revert CookieJarLib.ZeroAmount();
         if (currencyHeldByJar < amount) revert CookieJarLib.InsufficientBalance();
 
-        // Validate purpose requirement
-        if (STRICT_PURPOSE && bytes(purpose).length < 27) {
-            revert CookieJarLib.InvalidPurpose();
-        }
+        // Validate purpose requirement (uses Unicode code-point counting)
+        CookieJarValidation.validatePurpose(STRICT_PURPOSE, purpose);
 
         // Validate withdrawal amount
         if (WITHDRAWAL_OPTION == CookieJarLib.WithdrawalTypeOptions.Fixed) {