perf: check if it is already a BoxSource containing a CachedSource

[SyMind]

This PR refactors ReplaceSource and CachedSource to use trait objects (BoxSource) instead of generic type parameters, improving ergonomics and enabling runtime type checking. The key optimization checks if a BoxSource already wraps a CachedSource to avoid double-caching.

Key Changes:

• Converted ReplaceSource<T> and CachedSource<T> from generic structs to concrete structs using BoxSource
• Added optimization in CachedSource::new() to detect and unwrap existing CachedSource instances
• Removed original() methods from both structs since the inner source is now a trait object

[Copilot]

Pull Request Overview

This PR refactors ReplaceSource and CachedSource to use trait objects (BoxSource) instead of generic type parameters, improving ergonomics and enabling runtime type checking. The key optimization checks if a BoxSource already wraps a CachedSource to avoid double-caching.

Key Changes:

• Converted ReplaceSource<T> and CachedSource<T> from generic structs to concrete structs using BoxSource
• Added optimization in CachedSource::new() to detect and unwrap existing CachedSource instances
• Removed original() methods from both structs since the inner source is now a trait object

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/replace_source.rs	Converts ReplaceSource<T> to use BoxSource, removes Arc wrapper and original() method, simplifies trait implementations
src/cached_source.rs	Converts CachedSource<T> to use BoxSource, adds double-caching prevention logic, removes original() method

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[codspeed-hq]

CodSpeed Performance Report

Merging #183 will not alter performance

_{Comparing SyMind:perf-rm-inner-cached-source (94d18ea) with main (faf2138)}

Summary

✅ 9 untouched
⏩ 4 skipped¹

Footnotes

1. 4 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩