Performance: Parallelize data source fetching with structured concurrency

[leogdion]

Problem

DataSourcePipeline fetches data sources sequentially (lines 50-71), causing total sync time to equal the sum of all fetch times.

Current implementation:

do {
    restoreImages = try await fetchRestoreImages(options: options)
} catch { throw error }
do {
    xcodeVersions = try await fetchXcodeVersions(options: options)
} catch { throw error }

Proposed Solution

Use structured concurrency to fetch independent sources in parallel:

async let restoreImages = fetchRestoreImages(options: options)
async let xcodeVersions = fetchXcodeVersions(options: options)
async let swiftVersions = fetchSwiftVersions(options: options)

let (images, xcode, swift) = try await (restoreImages, xcodeVersions, swiftVersions)

Additionally:

• Add size limits for in-memory deduplication to prevent excessive memory usage
• Consider streaming/chunking for large datasets

Impact

Performance: Reduce sync time from sum(all sources) to max(source time)

Example: If 3 sources take 5s, 8s, and 3s:

• Current: 16 seconds total
• Parallel: 8 seconds total (50% faster)

Files Affected

• Examples/Bushel/Sources/BushelImages/DataSources/DataSourcePipeline.swift:50-71
• Deduplication methods (potential memory issues)

References

• PR update from writing blog post and examples MistKit#129 Review: update from writing blog post and examples MistKit#129 (comment)
• Section: Performance Considerations
• Related: Add comprehensive test suite for Bushel demo MistKit#136