Implement cloneConcurrency config

[cijiugechu]

Add new acceptance test that did not exist before for concurrency behavior in git clone flow.

[github-actions]

⏱️ Benchmark Results

Metric	Base	Head	Difference
Mean	2.528s	2.527s	-0.03% ✅
Median	2.536s	2.528s	-0.32% ✅
Min	2.364s	2.360s
Max	2.615s	2.710s
Std Dev	0.055s	0.078s

📊 Raw benchmark data

Base times: 2.527s, 2.539s, 2.471s, 2.469s, 2.577s, 2.530s, 2.548s, 2.520s, 2.553s, 2.433s, 2.534s, 2.598s, 2.471s, 2.571s, 2.615s, 2.567s, 2.535s, 2.364s, 2.550s, 2.485s, 2.576s, 2.482s, 2.508s, 2.604s, 2.516s, 2.594s, 2.473s, 2.550s, 2.537s, 2.541s

Head times: 2.710s, 2.689s, 2.475s, 2.500s, 2.589s, 2.559s, 2.532s, 2.402s, 2.520s, 2.460s, 2.501s, 2.569s, 2.519s, 2.591s, 2.626s, 2.583s, 2.484s, 2.544s, 2.604s, 2.535s, 2.523s, 2.455s, 2.360s, 2.535s, 2.505s, 2.547s, 2.418s, 2.565s, 2.419s, 2.493s

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Benchmark: gatsby install-full-cold

[greptile-apps]

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The implementation is clean and follows Rust best practices with proper RAII for semaphore permits. Validation prevents invalid config values, and comprehensive tests verify both config handling and actual concurrency limiting behavior. No issues found.
• No files require special attention

Important Files Changed

Filename	Overview
packages/zpm-config/schema.json	Added cloneConcurrency config field with type usize, default value 2
packages/zpm/src/project.rs	Added clone_limiter semaphore field and validation for cloneConcurrency >= 1
packages/zpm/src/git.rs	Acquire semaphore permit before git clone to enforce concurrency limit
tests/acceptance-tests/pkg-tests-specs/sources/commands/config/get.test.js	Added tests for cloneConcurrency default, configured value, and validation
tests/acceptance-tests/pkg-tests-specs/sources/protocols/git.test.ts	Added comprehensive test using git wrapper to verify concurrency limiting behavior

_{Last reviewed commit: d84dda0}