feat(cli): shorten file paths in tool output display

Add three-level path shortening hierarchy for cleaner CLI output:
1. Project path -> <project_name>/... (when project loaded via /project)
2. Workspace path -> ./... (relative to current working directory)
3. Home path -> ~/... (fallback for paths under home directory)

Changes:
- Add shorten_path() and shorten_paths_in_command() functions in display.rs
- Add project_path/project_name fields to ConsoleUiWriter
- Add set_workspace_path(), set_project_path(), clear_project() to UiWriter trait
- Add ui_writer() getter to Agent struct
- Wire up project path setting in /project and /unproject commands
- Set workspace path when creating agents in all CLI modes

Before: ● read_file | /Users/dhanji/icloud/butler/projects/appa_estate/status.md
After:  ● read_file | appa_estate/status.md (with project loaded)
        ● read_file | ./src/main.rs (workspace-relative)
        ● read_file | ~/Documents/file.txt (home-relative)

crates/g3-cli/src/accumulative.rs

@@ -15,6 +15,7 @@ use crate::cli_args::Cli;
 use crate::interactive::run_interactive;
 use crate::simple_output::SimpleOutput;
 use crate::ui_writer_impl::ConsoleUiWriter;
+use g3_core::ui_writer::UiWriter;
 use crate::utils::load_config_with_cli_overrides;
 
 /// Run accumulative autonomous mode - accumulates requirements from user input
@@ -153,6 +154,7 @@ pub async fn run_accumulative_mode(
 
                 // Create agent for this autonomous run
                 let ui_writer = ConsoleUiWriter::new();
+                ui_writer.set_workspace_path(workspace_dir.clone());
                 let agent = Agent::new_autonomous_with_readme_and_quiet(
                     config.clone(),
                     ui_writer,
@@ -284,6 +286,7 @@ async fn handle_command(
 
             // Create agent for interactive mode with requirements context
             let ui_writer = ConsoleUiWriter::new();
+            ui_writer.set_workspace_path(workspace_dir.clone());
             let agent = Agent::new_with_readme_and_quiet(
                 config,
                 ui_writer,