b69b24c107
Add three self-contained feature modules that plug into the root App model via shared state structs and render methods. setup.go -- First-run wizard with a 5-step flow: welcome screen, API key entry (password-masked text input), default time range selector (radio-style j/k navigation over 7/30/90 day options), theme picker (radio-style over all registered themes), and a completion screen that persists choices to ~/.config/cburn/config.toml. Gracefully handles save failures by noting the settings apply for the current session only. tab_sessions.go -- Session browser with two view modes: split view (1/3 condensed list + 2/3 detail pane, scrollable with offset tracking) and full-screen detail. The detail body shows duration, prompt/API-call ratio, per-type token breakdown with cache cost attribution, per-model API call table, and subagent indicator. tab_settings.go -- Runtime settings editor with 4 configurable fields (API key, theme, default days, monthly budget). Supports inline text input editing with Enter/Esc save/cancel flow, immediate config persistence, flash "Saved!" confirmation, and error display on save failure. Theme changes apply instantly without restart.