feat: add codetect-cli for MCP vs CLI token-cost A/B testing

[brian-lai]

Summary

• Adds codetect-cli binary providing the same 4 capabilities as the MCP server via direct CLI subcommands
• Enables A/B testing token consumption: MCP tools vs Bash tool invoking codetect-cli
• Reuses 100% of existing tool handler code via server.CallTool() — identical code paths, only transport differs

CLI Interface

codetect-cli search <query> [--top-k N] [--detail minimal|standard|rich]
codetect-cli file <path> [--start-line N] [--end-line N]
codetect-cli symbols find <name> [--kind KIND] [--limit N]
codetect-cli symbols list <path>
codetect-cli hybrid <query> [--limit N] [--rerank] [--detail minimal|standard|rich]

Changes

• cmd/codetect-cli/main.go — CLI entry point with subcommand routing (223 lines)
• cmd/codetect-cli/main_test.go — 24 tests covering arg parsing and tool invocation
• Makefile — Added build-cli target, updated build/install/uninstall

Test plan

• 24 unit tests pass (go test ./cmd/codetect-cli/...)
• make build-cli succeeds
• All 4 subcommands produce valid JSON output matching MCP tool format
• Graceful degradation when resources unavailable (symbols returns {"available": false})

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