fix: add missing jsonOutput parameter to SyncConfiguration

The configuration loader was not reading the BUSHEL_SYNC_JSON_OUTPUT
environment variable, even though it was set in the workflow. The
jsonOutput parameter was defined in ConfigurationKeys and
SyncConfiguration, but was missing from the loader initialization.

This caused the binary to output human-readable text instead of JSON,
which corrupted the sync-result.json file and caused jq parsing errors.

Root cause analysis:
1. Workflow set BUSHEL_SYNC_JSON_OUTPUT=true ✓
2. ConfigurationKeys.Sync.jsonOutput defined ✓
3. SyncConfiguration.jsonOutput parameter defined ✓
4. ConfigurationLoader reading jsonOutput ✗ (MISSING - now fixed)
5. SyncCommand checking config.sync?.jsonOutput ✓

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: leogdion

Sources/BushelCloudKit/Configuration/ConfigurationLoader+Loading.swift

@@ -94,7 +94,8 @@ extension ConfigurationLoader {
       verbose: read(ConfigurationKeys.Sync.verbose),
       force: read(ConfigurationKeys.Sync.force),
       minInterval: read(ConfigurationKeys.Sync.minInterval),
-      source: read(ConfigurationKeys.Sync.source)
+      source: read(ConfigurationKeys.Sync.source),
+      jsonOutput: read(ConfigurationKeys.Sync.jsonOutput)
     )
 
     // Export command configuration