## 1. Specification
- [x] 1.1 Define configurable initial prompt and project instruction append behavior.

## 2. Implementation
- [x] 2.1 Add `Agent.InitialPrompt` setting with the current prompt in appsettings.
- [x] 2.2 Keep the current prompt as the code default when no setting is configured.
- [x] 2.3 Build summary agent instructions by appending `AGENTS.md` content for bound projects.
- [x] 2.4 Use the built instructions when creating the summary agent.

## 3. Validation
- [x] 3.1 Test configurable prompt fallback and override behavior.
- [x] 3.2 Test project `AGENTS.md` instruction appendix formatting.
- [x] 3.3 Run targeted and full tests.