TUI: Add session resume picker (--resume) and quick resume (--continue) (#3135)

Adds a TUI resume flow with an interactive picker and quick resume.

- CLI: 
  - --resume / -r: open picker to resume a prior session
  - --continue   / -l: resume the most recent session (no picker)
- Behavior on resume: initial history is replayed, welcome banner
hidden, and the first redraw is suppressed to avoid flicker.
- Implementation:
- New tui/src/resume_picker.rs (paginated listing via
RolloutRecorder::list_conversations)
  - App::run accepts ResumeSelection; resumes from disk when requested
- ChatWidget refactor with ChatWidgetInit and new_from_existing; replays
initial messages
- Tests: cover picker sorting/preview extraction and resumed-history
rendering.
- Docs: getting-started updated with flags and picker usage.



https://github.com/user-attachments/assets/1bb6469b-e5d1-42f6-bec6-b1ae6debda3b

codex-rs/tui/src/cli.rs

@@ -13,6 +13,30 @@ pub struct Cli {
     #[arg(long = "image", short = 'i', value_name = "FILE", value_delimiter = ',', num_args = 1..)]
     pub images: Vec<PathBuf>,
 
+    /// Open an interactive picker to resume a previous session recorded on disk
+    /// instead of starting a new one.
+    ///
+    /// Notes:
+    /// - Mutually exclusive with `--continue`.
+    /// - The picker displays recent sessions and a preview of the first real user
+    ///   message to help you select the right one.
+    #[arg(long = "resume", default_value_t = false, conflicts_with = "continue")]
+    pub resume: bool,
+
+    /// Continue the most recent conversation without showing the picker.
+    ///
+    /// Notes:
+    /// - Mutually exclusive with `--resume`.
+    /// - If no recorded sessions are found, this behaves like starting fresh.
+    /// - Equivalent to picking the newest item in the resume picker.
+    #[arg(
+        id = "continue",
+        long = "continue",
+        default_value_t = false,
+        conflicts_with = "resume"
+    )]
+    pub r#continue: bool,
+
     /// Model the agent should use.
     #[arg(long, short = 'm')]
     pub model: Option<String>,