Remove automatic README loading from context window

README.md is no longer auto-loaded into the LLM context at startup.
This saves ~4,600 tokens per session while AGENTS.md and memory.md
still provide all critical information for code tasks.

Changes:
- Delete read_project_readme() function
- Remove readme_content parameter from combine_project_content()
- Rename extract_readme_heading() -> extract_project_heading()
- Rename Agent constructors: *_with_readme_* -> *_with_project_context_*
- Update context preservation to only check for Agent Configuration
- Remove has_readme field from LoadedContent
- Update all tests to use new markers and function names

The LLM can still read README.md on-demand via read_file when needed.

crates/g3-core/tests/project_context_test.rs

@@ -1,6 +1,6 @@
 //! Integration tests for project context loading and ordering.
 //!
-//! Tests that the context window has the correct structure when projects are loaded.
+//! Tests that the context window has the correct structure when project context is loaded.
 //! Also tests that project content survives compaction.
 
 use g3_core::{
@@ -11,7 +11,7 @@ use g3_config::Config;
 use g3_providers::{mock::MockProvider, ProviderRegistry, MockResponse, MessageRole};
 
 /// Helper to create a test agent with mock provider
-async fn create_test_agent(readme_content: Option<String>) -> Agent<NullUiWriter> {
+async fn create_test_agent(project_context: Option<String>) -> Agent<NullUiWriter> {
     let config = Config::default();
     let provider = MockProvider::new()
         .with_response(MockResponse::text("Test response"));
@@ -19,7 +19,7 @@ async fn create_test_agent(readme_content: Option<String>) -> Agent<NullUiWriter
     let mut registry = ProviderRegistry::new();
     registry.register(provider);
     
-    Agent::new_for_test_with_readme(config, NullUiWriter, registry, readme_content)
+    Agent::new_for_test_with_project_context(config, NullUiWriter, registry, project_context)
         .await
         .expect("Failed to create test agent")
 }
@@ -337,7 +337,7 @@ async fn create_agent_with_mock_and_readme(
     let mut registry = ProviderRegistry::new();
     registry.register(provider);
     
-    Agent::new_for_test_with_readme(config, NullUiWriter, registry, readme_content)
+    Agent::new_for_test_with_project_context(config, NullUiWriter, registry, readme_content)
         .await
         .expect("Failed to create test agent")
 }

crates/g3-core/tests/test_acd_integration.rs

@@ -104,9 +104,9 @@ fn test_reset_with_summary_and_stub_no_stub() {
     assert!(has_summary, "Should have summary");
 }
 
-/// Test that README message is preserved during reset
+/// Test that project context message is preserved during reset
 #[test]
-fn test_reset_preserves_readme() {
+fn test_reset_preserves_project_context() {
     let mut context = ContextWindow::new(100000);
     
     // Add system prompt
@@ -115,10 +115,10 @@ fn test_reset_preserves_readme() {
         "You are a helpful assistant.".to_string(),
     ));
     
-    // Add README message (second system message with specific content)
+    // Add project context message (second system message with Agent Configuration)
     context.add_message(Message::new(
         MessageRole::System,
-        "Project README: This is a test project.".to_string(),
+        "🤖 Agent Configuration (from AGENTS.md):\nTest agent config.".to_string(),
     ));
     
     // Add conversation
@@ -133,11 +133,11 @@ fn test_reset_preserves_readme() {
         Some(stub),
     );
     
-    // README should be preserved
-    let has_readme = context.conversation_history.iter().any(|m| 
-        m.content.contains("Project README")
+    // Project context should be preserved
+    let has_project_context = context.conversation_history.iter().any(|m| 
+        m.content.contains("Agent Configuration")
     );
-    assert!(has_readme, "README message should be preserved");
+    assert!(has_project_context, "Project context message should be preserved");
 }
 
 /// Test fragment chain integrity

crates/g3-core/tests/test_agent_session_id.rs

@@ -15,7 +15,7 @@ use tempfile::TempDir;
 async fn create_test_agent(temp_dir: &TempDir) -> Agent<NullUiWriter> {
     std::env::set_current_dir(temp_dir.path()).unwrap();
     let config = Config::default();
-    Agent::new_with_readme_and_quiet(config, NullUiWriter, None, true)
+    Agent::new_with_project_context_and_quiet(config, NullUiWriter, None, true)
         .await
         .unwrap()
 }
@@ -24,7 +24,7 @@ async fn create_test_agent(temp_dir: &TempDir) -> Agent<NullUiWriter> {
 async fn create_agent_mode_agent(temp_dir: &TempDir, agent_name: &str) -> Agent<NullUiWriter> {
     std::env::set_current_dir(temp_dir.path()).unwrap();
     let config = Config::default();
-    let mut agent = Agent::new_with_readme_and_quiet(config, NullUiWriter, None, true)
+    let mut agent = Agent::new_with_project_context_and_quiet(config, NullUiWriter, None, true)
         .await
         .unwrap();
     agent.set_agent_mode(agent_name);

crates/g3-core/tests/test_reset_with_summary.rs

@@ -54,18 +54,18 @@ fn test_reset_with_summary_preserves_system_prompt() {
     assert!(has_user_msg, "Should have the latest user message");
 }
 
-/// Test that reset_with_summary preserves README message if present
+/// Test that reset_with_summary preserves project context message if present
 #[test]
-fn test_reset_with_summary_preserves_readme() {
+fn test_reset_with_summary_preserves_project_context() {
     let mut context = ContextWindow::new(10000);
 
     // Add the system prompt as the first message
     let system_prompt = "You are G3, an AI programming agent...";
     context.add_message(Message::new(MessageRole::System, system_prompt.to_string()));
 
-    // Add README as second system message
-    let readme_content = "# Project README\n\nThis is a test project.";
-    context.add_message(Message::new(MessageRole::System, readme_content.to_string()));
+    // Add project context as second system message (with Agent Configuration marker)
+    let project_context = "🤖 Agent Configuration (from AGENTS.md):\n\nTest agent config.";
+    context.add_message(Message::new(MessageRole::System, project_context.to_string()));
 
     // Add some conversation history
     context.add_message(Message::new(MessageRole::User, "Task: Write a function".to_string()));
@@ -85,15 +85,15 @@ fn test_reset_with_summary_preserves_readme() {
         "First message should be the system prompt"
     );
 
-    // Verify the README was preserved as the second message
+    // Verify the project context was preserved as the second message
     let second_message = &context.conversation_history[1];
     assert!(
         matches!(second_message.role, MessageRole::System),
         "Second message should be a System message"
     );
     assert!(
-        second_message.content.contains("Project README"),
-        "Second message should be the README"
+        second_message.content.contains("Agent Configuration"),
+        "Second message should be the project context"
     );
 }