Inject working directory into context to prevent path hallucinations

The LLM often hallucinates incorrect paths like /Users/jnbrymn/GitHub/g3
when the actual working directory is different. This causes wasted tokens
and failed commands as the LLM tries cd commands that fail.

Fix: Add the current working directory to the combined project content
that gets injected into the context at startup. This appears as:

  📂 Working Directory: /actual/path/to/workspace

This is prepended before AGENTS.md, README.md, and project memory,
so the LLM knows the correct path from the start.

crates/g3-cli/src/agent_mode.rs

@@ -181,6 +181,7 @@ pub async fn run_agent_mode(
         agents_content_opt,
         readme_content_opt,
         memory_content_opt,
+        &workspace_dir,
     );
 
     // Create agent with custom system prompt