Rename: PreambleBuilder to SystemPromptBuilder

This commit renames the builder throughout the codebase to better reflect its purpose.
The PreambleBuilder was effectively building system prompts for LLM agents, and this new name
makes the intent clearer to developers familiar with LLM terminology.

Changes:
- Core: Renamed preamble.rs module to system_prompt.rs
- Core: Renamed PreambleBuilder struct to SystemPromptBuilder
- Core: Updated all documentation and examples to use system_prompt terminology
- Core: Renamed preamble_preview.rs example to system_prompt_preview.rs
- Rig: Updated re-exports and documentation
- Rig: Updated examples to use SystemPromptBuilder
- SerdesAI: Updated re-exports and documentation
- SerdesAI: Updated examples to use SystemPromptBuilder

Git history preserved via git mv for preamble.rs -> system_prompt.rs rename.

All unit tests pass (119 passed)
All doctests pass (13 passed)

Author: Sewer56

…-tools-core/examples/preamble_preview.rs …s-core/examples/system_prompt_preview.rssrc/llm-coding-tools-core/examples/preamble_preview.rs renamed to src/llm-coding-tools-core/examples/system_prompt_preview.rs src/llm-coding-tools-core/examples/preamble_preview.rs renamed to src/llm-coding-tools-core/examples/system_prompt_preview.rs

@@ -1,23 +1,23 @@
-//! Preamble preview - demonstrates full preamble generation.
+//! System Prompt preview - demonstrates full system prompt generation.
 //!
-//! Shows how PreambleBuilder combines:
+//! Shows how SystemPromptBuilder combines:
 //! - Custom system prompts
 //! - Environment section (working directory, allowed paths)
 //! - Tool usage guidelines (from tracked tools)
 //! - Supplemental context (git workflow, GitHub CLI)
 //!
-//! Run: cargo run --example preamble_preview -p llm-coding-tools-core
+//! Run: cargo run --example system_prompt_preview -p llm-coding-tools-core
 
 use llm_coding_tools_core::context::ToolContext;
-use llm_coding_tools_core::{context, AllowedPathResolver, PreambleBuilder};
+use llm_coding_tools_core::{context, AllowedPathResolver, SystemPromptBuilder};
 
 fn main() {
     // Use from_canonical to avoid filesystem requirements for the example.
     // In real usage, AllowedPathResolver::new() canonicalizes and validates paths.
     let resolver = AllowedPathResolver::from_canonical(["/home/user/project", "/tmp"]);
 
-    // Build preamble with all features demonstrated
-    let mut pb = PreambleBuilder::new()
+    // Build system prompt with all features demonstrated
+    let mut pb = SystemPromptBuilder::new()
         .system_prompt(
             "# System Instructions\n\n\
              You are a helpful coding assistant. Follow best practices and \

src/llm-coding-tools-core/src/context/mod.rs

@@ -29,13 +29,13 @@ pub const BASH: &str = include_str!("bash.txt");
 /// Git workflow context - commit creation guidance.
 ///
 /// Supplemental context for agents using git via the Bash tool.
-/// Include via [`PreambleBuilder::add_context`](crate::PreambleBuilder::add_context).
+/// Include via [`SystemPromptBuilder::add_context`](crate::SystemPromptBuilder::add_context).
 pub const GIT_WORKFLOW: &str = include_str!("git_workflow.txt");
 
 /// GitHub CLI context - gh command usage guidance.
 ///
 /// Supplemental context for agents using the GitHub CLI via the Bash tool.
-/// Include via [`PreambleBuilder::add_context`](crate::PreambleBuilder::add_context).
+/// Include via [`SystemPromptBuilder::add_context`](crate::SystemPromptBuilder::add_context).
 pub const GITHUB_CLI: &str = include_str!("github_cli.txt");
 
 /// Todo read tool context - reading task lists.
@@ -77,10 +77,10 @@ pub const GREP_ABSOLUTE: &str = include_str!("grep_absolute.txt");
 /// Grep tool context for allowed/sandboxed path mode.
 pub const GREP_ALLOWED: &str = include_str!("grep_allowed.txt");
 
-/// Trait for tools that provide usage context for LLM preambles.
+/// Trait for tools that provide usage context for LLM system prompts.
 ///
-/// Implement this trait on tool types (for frameworks like rig) to enable automatic preamble
-/// generation via [`PreambleBuilder`](crate::PreambleBuilder).
+/// Implement this trait on tool types (for frameworks like rig) to enable automatic system prompt
+/// generation via [`SystemPromptBuilder`](crate::SystemPromptBuilder).
 ///
 /// # Example
 ///
@@ -98,13 +98,13 @@ pub const GREP_ALLOWED: &str = include_str!("grep_allowed.txt");
 /// }
 /// ```
 pub trait ToolContext {
-    /// Tool name used for section headers in generated preamble.
+    /// Tool name used for section headers in generated system prompt.
     ///
     /// Should be lowercase (e.g., "read", "bash", "glob").
-    /// PreambleBuilder capitalizes this for display.
+    /// SystemPromptBuilder capitalizes this for display.
     const NAME: &'static str;
 
-    /// Returns the tool's context string for preamble generation.
+    /// Returns the tool's context string for system prompt generation.
     ///
     /// This should return one of the context constants from this module.
     fn context(&self) -> &'static str;

src/llm-coding-tools-core/src/lib.rs

@@ -14,15 +14,15 @@ pub mod fs;
 pub mod operations;
 pub mod output;
 pub mod path;
-pub mod preamble;
+pub mod system_prompt;
 pub mod tool_names;
 pub mod util;
 
 pub use context::ToolContext;
 pub use error::{ToolError, ToolResult};
 pub use output::ToolOutput;
 pub use path::{AbsolutePathResolver, AllowedPathResolver, PathResolver};
-pub use preamble::{PreambleBuilder, Substitute};
+pub use system_prompt::{Substitute, SystemPromptBuilder};
 
 // Re-export operations (always available, sync or async based on runtime feature)
 pub use operations::{