feat(prompts): integrate top_agent module from PR #20

- Add top_agent.rs with TopAgentPromptBuilder, TopAgentPresets, and ~20 section constants
- Update mod.rs to include top_agent module and re-export public types
- Integrates PR #20's top-agent prompts into PR #21's skill-based architecture

Author: echobt

src/cortex-prompt-harness/src/prompts/mod.rs

@@ -19,6 +19,7 @@
 //! - [`review`]: Code review prompts
 //! - [`tools`]: Tool-specific prompts (subagent executor, mentions)
 //! - [`generation`]: Agent generation prompts
+//! - [`top_agent`]: Top-agent style prompts (autonomous, backup-first philosophy)
 //!
 //! # Usage
 //!
@@ -34,6 +35,10 @@
 //!
 //! // Get task prompts
 //! let summary = prompts::tasks::SUMMARIZATION_PROMPT;
+//!
+//! // Use top-agent style prompts
+//! let top_agent = prompts::top_agent::TOP_AGENT_SYSTEM_PROMPT;
+//! let coding = prompts::top_agent::TopAgentPresets::coding_assistant();
 //! ```
 
 pub mod agents;
@@ -44,6 +49,7 @@ pub mod generation;
 pub mod review;
 pub mod tasks;
 pub mod tools;
+pub mod top_agent;
 
 // Re-export commonly used prompts for convenience
 pub use agents::{
@@ -66,3 +72,6 @@ pub use builtin_skills::{
     list_builtin_skills,
 };
 pub use tasks::{COMPACTION_PROMPT, SUMMARIZATION_PROMPT};
+pub use top_agent::{
+    TOP_AGENT_SECTION_NAMES, TOP_AGENT_SYSTEM_PROMPT, TopAgentPresets, TopAgentPromptBuilder,
+};