cli: run warm proxy queries concurrently

[justrach]

Summary

• replace the POSIX warm CLI proxy's sequential query dispatch with a bounded eight-way dispatcher
• drain accepted work before a version/handoff retirement so Explorer/Store lifetimes stay safe
• preserve the existing Windows named-pipe behavior until it has equivalent bounded ownership handoff
• add a regression test for the concurrency gate

Why

The production embeddings origin is not the current bottleneck: it sustained 32 concurrent 25-input requests (800 embeddings) in 161.6 ms with 100% success. Agent-style codedb context calls were instead stair-stepping because the per-project warm CLI daemon handled one connection at a time.

Benchmark

Eight concurrent hybrid context calls on macOS, same workload:

	Before	After
Successes	8/8	8/8
Wall time	6.44 s	2.69 s
Median latency	3.30 s	2.18 s
Worst latency	6.43 s	2.68 s

This reduces concurrent wall time by about 58%. The GPU reported no new overload failures.

Verification

• zig build test
• python3 scripts/e2e_mcp_test.py --binary zig-out/bin/codedb --project /Users/blackfloofie/tmp/codedb-cli-concurrency (76/76 passed)
• live eight-way hybrid context benchmark (8/8 passed)
• direct origin concurrency matrix through 32 simultaneous requests (all passed)

[github-actions]

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[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-08-29T04:17:32.075267Z	09ada3d	PR opened

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