refactor: deduplicate loop bringup by extracting send-loop-prompt and section-bootstrap

[chriswritescode-dev]

Summary

Deduplicates loop bringup logic by extracting sendLoopPrompt and sectionBootstrap into their own modules, reducing duplication between runtime.ts and execution.ts.

Changes

Added

• src/loop/send-loop-prompt.ts — extracted send-loop-prompt logic
• src/services/section-bootstrap.ts — extracted section bootstrap logic
• test/loop/send-loop-prompt.test.ts — test coverage for send-loop-prompt
• test/services/section-bootstrap.test.ts — test coverage for section bootstrap

Updated

• src/loop/runtime.ts — refactored to use extracted modules (-98 lines)
• src/services/execution.ts — refactored to use extracted modules (-169 lines)
• vitest.config.ts — test config update

Removed

• Duplicated loop bringup logic between runtime.ts and execution.ts

Breaking changes

None.