refactor: extract ANSI strip helper and improve worktree list format

Deduplicate the ANSI-stripping sed pattern into _forgit_strip_ansi
and adopt the [XY] bracket prefix style (consistent with ga) for
worktree list output. The Y position now encodes both lock (L) and
prunable (P) states, with L taking precedence when both present.

Author: wfxr

README.md

@@ -195,14 +195,17 @@ If you're having issues after updating, and commands such as `forgit::add` or al
 | <kbd>Alt</kbd> - <kbd>W</kbd>                 | Toggle preview wrap                         |
 | <kbd>Ctrl</kbd> - <kbd>S</kbd>                | Toggle sort                                 |
 | <kbd>Ctrl</kbd> - <kbd>R</kbd>                | Toggle selection                            |
-| <kbd>Ctrl</kbd> - <kbd>Y</kbd>                | Copy commit hash/stash ID/worktree path*    |
+| <kbd>Ctrl</kbd> - <kbd>Y</kbd>                | Copy commit hash/stash ID/worktree path<sup>1</sup> |
 | <kbd>Ctrl</kbd> - <kbd>K</kbd> / <kbd>P</kbd> | Selection move up                           |
 | <kbd>Ctrl</kbd> - <kbd>J</kbd> / <kbd>N</kbd> | Selection move down                         |
 | <kbd>Alt</kbd> - <kbd>K</kbd> / <kbd>P</kbd>  | Preview move up                             |
 | <kbd>Alt</kbd> - <kbd>J</kbd> / <kbd>N</kbd>  | Preview move down                           |
 | <kbd>Alt</kbd> - <kbd>E</kbd>                 | Open file in default editor (when possible) |
+| <kbd>Alt</kbd> - <kbd>L</kbd>                 | Toggle worktree lock/unlock<sup>2</sup>              |
+
+<sup>1</sup> Available when the selection contains a commit hash, stash ID, or worktree path.
+<sup>2</sup> Only available in the worktree browser (`gw`).
 
-\* Available when the selection contains a commit hash, stash ID, or worktree path.
 For Linux users `FORGIT_COPY_CMD` should be set to make copy work. Example: `FORGIT_COPY_CMD='xclip -selection clipboard'`.
 
 # ⚙ Options