fix(05-jamtrack): require sample rate match and fix error boundary

Two critical fixes:

1. Error Boundary Crash
   - errorInfo can be null between getDerivedStateFromError and componentDidCatch
   - Added null check: {this.state.errorInfo && this.state.errorInfo.componentStack}
   - Prevents "Cannot read properties of null" error

2. Sample Rate Mismatch
   - Removed fallback to different sample rates (tier 4)
   - Native client CANNOT play packages with mismatched sample rates
   - If client is 44kHz but package is 48kHz, play will fail with "Unable to play JamTrack"
   - Now throws clear error: "No package available for sample rate 44kHz. Available rates: 48kHz"

Root cause of play failure:
- Client sample rate: 44kHz (from GetSampleRate 44.099998...)
- Package downloaded: 48kHz (only available package)
- fqId built: jamTrack.id-44 (based on client rate)
- Native client cannot play 48kHz files with 44kHz fqId → Play fails

Solution:
- Sample rate fallback removed - must match exactly
- User gets actionable error message suggesting to restart audio interface
  or select different sample rate

Fixes "Unable to play JamTrack" error and error boundary crash.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

jam-ui/src/components/common/ErrorBoundary.js

@@ -33,7 +33,7 @@ class ErrorBoundary extends React.Component {
               <pre className="mt-2 text-white">
                 {this.state.error && this.state.error.toString()}
                 <br />
-                {this.state.errorInfo.componentStack}
+                {this.state.errorInfo && this.state.errorInfo.componentStack}
               </pre>
             </details>
           )}

jam-ui/src/store/features/mediaSlice.js

@@ -88,11 +88,11 @@ export const downloadJamTrack = createAsyncThunk(
       }
 
       // pickMyPackage logic with fallback strategy
-      // Preference order:
-      // 1. ogg + jkz encryption + matching sample rate (ideal)
-      // 2. ogg + any encryption + matching sample rate
-      // 3. any format + matching sample rate
-      // 4. any package (last resort)
+      // CRITICAL: Sample rate MUST match - native client cannot play mismatched rates
+      // Preference order for matching sample rate:
+      // 1. ogg + jkz encryption (ideal for security)
+      // 2. ogg + any/no encryption (preferred format)
+      // 3. any format (mp3, etc.)
 
       let compatiblePackage = null;
 
@@ -118,14 +118,10 @@ export const downloadJamTrack = createAsyncThunk(
         );
       }
 
-      // Try 4: Just use first available package
+      // No fallback to different sample rates - client cannot play mismatched rates
       if (!compatiblePackage) {
-        compatiblePackage = mixdown.packages[0];
-        console.warn(`[JamTrack] No package matches sample rate ${sampleRate}kHz, using first available package (${compatiblePackage.file_type}, ${compatiblePackage.sample_rate}kHz)`);
-      }
-
-      if (!compatiblePackage) {
-        throw new Error(`No packages available for mixdown "${mixdown.name}"`);
+        const availableRates = mixdown.packages.map(p => p.sample_rate).join(', ');
+        throw new Error(`No package available for sample rate ${sampleRate}kHz. Available rates: ${availableRates}kHz. Try restarting your audio interface or selecting a different sample rate.`);
       }
 
       const packageId = compatiblePackage.id;