Feature request: to add a keyboard-first, searchable code picker for selected text. #1493

Is your feature request related to a problem? Please describe.

The current Recent Codes is useful:

• User selects text
• User presses R
• User can use arrow keys to focus on code, then press enter to select

However, it is limited to recently used codes. In projects with larger codebooks, it would useful to have a feature that can search and apply codes without moving to the mouse, hovering over the sidebar, scrolling, and then returning to the keyboard. For keyboard-first users, this would save a lot of time to have a feature with similar behavior to Recent Codes.

Describe the solution you'd like

The proposed workflow could look like this:

• User selects text
• User presses F
• User types part of a code, a search box populates with code names, user focuses on populated terms with arrow keys, then presses enter to input code

I envisioned this like Zotero's citation picker functionality (or, similar to searching for something in Finder, or command palettes in various apps).

• In the Code Text editor view, user selects text, then presses F
• A new dialogue box appears, with a search text field, which is in focus automatically
• In the same dialogue box, underneath the search search text field, is a box in which all codes are displayed
• The code box is filtered live as a user types in the search text field, searching for their intended code
• Up/down arrows change the highlighted returned code, while typing focus remains in the search text field
• Enter applies the highlighted code to the text, and also closes the dialogue box
• Escape cancels the dialogue box

Describe alternatives you've considered
I realized after completing an initial local prototype (I was excited to play around with Python), that the contributor guidelines ask contributors to discuss an issue and wait for assignment before opening a pull request. I do not want to get ahead of the projects process, so I am opening this issue first and will not submit a PR unless the feature is welcome and/or assigned.

I have a locally-tested implementation on a separate branch. It was tested on macOS Tahoe 26.5.2, running QualCoder from source.

Additional context
Add any other context or screenshots about the feature request here.