feat(bench): add dhat heap profiling examples

[bug-ops]

Summary

• Add dhat_extraction example for profiling heap allocations during TAR/ZIP extraction
• Add dhat_creation example for profiling heap allocations during TAR/TAR.GZ/ZIP creation
• Add dhat-heap.json to .gitignore
• Remove unused lru dependency

Usage

cargo run -p exarch-core --example dhat_extraction --release -- zip
cargo run -p exarch-core --example dhat_creation --release -- tar

Open dhat-heap.json at https://nnethercote.github.io/dh_view/dh_view.html

Initial results (500 files x 1 KB)

Operation	Total Allocated	Peak Live
TAR extraction	33.2 MB	72 KB
ZIP extraction	44.4 MB	275 KB
TAR creation	326 KB	152 KB
ZIP creation	207.2 MB	827 KB

Test plan

• cargo clippy passes
• Both examples compile and run in release mode
• Zero bytes at t-end (no memory leaks)

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

@@            Coverage Diff             @@
##             main      #49      +/-   ##
==========================================
+ Coverage   90.08%   90.13%   +0.05%     
==========================================
  Files          61       57       -4     
  Lines       10013     9846     -167     
==========================================
- Hits         9020     8875     -145     
+ Misses        993      971      -22     

Flag	Coverage Δ
exarch-python	?

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