Fix confusing documentation references

1. architecture.md: Fixed diagram to show 'studio' instead of 'g3-console'
   (the crate was renamed during development)

2. analysis/memory.md: Removed reference to non-existent machine_ui_writer.rs

3. theme.rs: Clarified that 'retro' is a theme option (the default theme),
   not a separate TUI mode. No --retro CLI flag exists.

analysis/memory.md

@@ -56,7 +56,6 @@
 ### UI Abstraction Layer
 - `crates/g3-core/src/ui_writer.rs` [0..4500] - `UiWriter` trait, `NullUiWriter`
 - `crates/g3-cli/src/ui_writer_impl.rs` [0..14000] - `ConsoleUiWriter` implementation
-- `crates/g3-cli/src/machine_ui_writer.rs` [0..4000] - `MachineUiWriter` implementation
 - `crates/g3-cli/src/simple_output.rs` [0..1200] - `SimpleOutput` helper (separate from UiWriter)
 
 ### Feedback Extraction

crates/g3-cli/src/theme.rs

@@ -4,7 +4,11 @@ use std::fs;
 use std::path::Path;
 use anyhow::Result;
 
-/// Color theme configuration for the retro TUI
+/// Color theme configuration for the TUI.
+/// 
+/// Note: The "retro" theme is the default theme (inspired by Alien terminals).
+/// This is a theme option, not a separate TUI mode. The theme can be selected
+/// via config file or the `from_name()` method ("default" and "retro" are equivalent).
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct ColorTheme {
     /// Name of the theme

docs/architecture.md

@@ -49,8 +49,7 @@ G3 follows a **tool-first philosophy**: instead of just providing advice, it act
          ┌───────────────────────┼───────────────────────┐
          │                       │                       │
 ┌─────────────────┐    ┌─────────────────┐
-│ g3-ensembles    │    │   g3-console    │
+│ g3-ensembles    │    │     studio      │
-│                 │    │   studio        │
 │ • Flock mode    │    │                 │
 │ • Multi-agent   │    │ • Worktree mgmt │
 │ • Parallel dev  │    │ • Session mgmt  │