feat: add scramble flag for development text scrambling

This commit introduces a new scramble option to help reduce distractions
during development by scrambling text using rot13. When enabled via the
new `--scramble` flag, text displayed in various views is transformed,
making it easier to focus on layout and behavior without reading the
actual content.

App & Args Updates

  - Added a `scramble: bool` field to the main application state (in `app.rs`).

  - Extended argument parsing (in `args.rs`) to recognize the `--scramble` flag.

NoteOptions Enhancement

  - Introduced a new bit flag `scramble_text` in `NoteOptions` with
    corresponding setter/getter methods.

UI Adjustments

  - Propagated the scramble flag through note rendering functions across
    navigation, timeline, and note view modules.

  - Updated several UI components (e.g., in `nav.rs`, `route.rs`, and
    `contents.rs`) to accept and apply the new note options.

Rot13 Implementation

  - Implemented a helper function (`rot13`) to scramble text
    conditionally when the scramble option is enabled.

This feature is intended for development builds only, offering a way to
obscure text content during UI tweaks and testing.

Signed-off-by: William Casarin <jb55@jb55.com>

crates/notedeck_columns/src/args.rs

@@ -8,6 +8,7 @@ pub struct ColumnsArgs {
     pub columns: Vec<ArgColumn>,
     pub since_optimize: bool,
     pub textmode: bool,
+    pub scramble: bool,
 }
 
 impl ColumnsArgs {
@@ -17,6 +18,7 @@ impl ColumnsArgs {
             columns: vec![],
             since_optimize: true,
             textmode: false,
+            scramble: false,
         };
 
         let mut i = 0;
@@ -28,6 +30,8 @@ impl ColumnsArgs {
                 res.textmode = true;
             } else if arg == "--no-since-optimize" {
                 res.since_optimize = false;
+            } else if arg == "--scramble" {
+                res.scramble = true;
             } else if arg == "--filter" {
                 i += 1;
                 let filter = if let Some(next_arg) = args.get(i) {