Replace 'precision' with 'resolution' across site, add negative-input validation

Fix remaining 'precision' wording in the homepage Gas Savings card and
README header. Add shift/targetBits range checks in the playground so
negative or zero values show an error message immediately.

Author: 0xferit

README.md

@@ -3,7 +3,7 @@
 [![Staking Case: Gas Usage Reduction](https://img.shields.io/endpoint?url=https://raw.githubusercontent.com/0xferit/uint-quantization-lib/gh-badges/.badges/staking-savings.json)](test/showcase/ShowcaseGas.t.sol)
 [![Extreme Case: Gas Usage Reduction](https://img.shields.io/endpoint?url=https://raw.githubusercontent.com/0xferit/uint-quantization-lib/gh-badges/.badges/extreme-savings.json)](test/showcase/ShowcaseGas.t.sol)
 
-Token amounts carry 18 decimals of precision. Timestamps fit in 40 bits but live in `uint64`. Oracle prices, counters, accumulated fees: most on-chain values use far more resolution than the application needs, and every extra storage slot costs 20,000 gas on a cold write.
+Token amounts carry 18 decimals of resolution. Timestamps fit in 40 bits but live in `uint64`. Oracle prices, counters, accumulated fees: most on-chain values use far more resolution than the application needs, and every extra storage slot costs 20,000 gas on a cold write.
 
 This library quantizes `uint256` values via right-shift compression, packing more fields per storage slot and cutting gas on every write.
 

index.html

@@ -163,7 +163,7 @@ <h2 class="section-title sr">Why Quantization?</h2>
       <div class="card-grid">
         <div class="card sr" style="transition-delay:0.1s">
           <h3>Gas Savings</h3>
-          <p>Compress values that don't need full uint256 precision so more fields fit per storage slot, cutting SSTORE/SLOAD costs.</p>
+          <p>Compress values that don't need full uint256 resolution so more fields fit per storage slot, cutting SSTORE/SLOAD costs.</p>
         </div>
       </div>
     </section>

playground.html

@@ -395,6 +395,8 @@
 
     function fieldError(f) {
       if (!f.quantized) return '';
+      if (f.shift < 0) return 'shift must be non-negative';
+      if (f.targetBits < 1) return 'targetBits must be at least 1';
       if (f.shift + f.targetBits > 256) return 'shift + targetBits exceeds 256';
       if (ceilTo8(f.targetBits) >= f.bits) return 'quantized type must be smaller than original';
       return '';