perf(runtime): reuse invocation Container client

[stephenlclarke]

Summary

• lazily reuse one control-plane ContainerClient across a Compose invocation
• keep attach and exec sessions on dedicated clients because disconnect owns their XPC connection
• preserve the public dependency-construction API and parser/help laziness
• add concurrency, isolation, and laziness coverage for the client pool

Evidence

• focused runtime proof: 19 tests in 4 suites passed
• 100 concurrent control requests construct exactly one client
• session clients remain distinct; dependency construction creates no XPC client
• strict SwiftLint, SwiftFormat, and git diff --check: passed
• exact matched-stack release benchmark: 84/84 operations passed; functional parity PASS; 10x guard PASS
• median startup changes versus retained evidence: 1 service -5.3%, 10 services +10.0%, 50 services +13.2%
• median teardown changes: 1 service +5.2%, 10 services -1.5%, 50 services -1.9%

The timing result is mixed, so this PR claims reduced XPC connection construction/churn and resource ownership—not a latency improvement. Raw evidence was produced with identical Container 731f195c and Containerization 97049499 sources, release configuration, images, Docker reference, host, fixtures, and counterbalanced seven-run schedule.

Compatibility

• public ComposeContainerRuntime.dependencies call shapes are preserved
• help/parser-only paths remain lazy and do not activate Container XPC
• attach and exec cancellation/disconnect semantics retain connection isolation

Related work

• contributes to [Parity] Comparable-or-better same-host performance #278; does not close it
• shared/pre-warmed isolation remains a separate explicit product contract

[stephenlclarke]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Nice work!

Reviewed commit: 4ae1f92210

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[stephenlclarke]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 👍

Reviewed commit: 10a35f7e15

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".