feat: cycle command completions backward with Shift+Tab

docs/editing.md

@@ -51,7 +51,7 @@ Indicators refresh asynchronously. Typing and undo/redo retain the last complete
 | Insert | Type, Enter, Tab, Backspace/Delete, arrows, Home/End at every caret outside snippets; Esc returns to Normal, retaining carets |
 | Insert | Ctrl+n requests completion at the primary caret or cycles next; Ctrl+j/k cycles next/previous while completion is open |
 | Insert, active snippet | Type to replace the highlighted argument and its mirrors; Tab / Shift+Tab moves next/previous |
-| Command | Tab completes/cycles command names; Enter executes; ↑/↓ or Ctrl+k/j browse history; Backspace edits; Esc cancels |
+| Command | Tab / Shift+Tab completes/cycles command names forward/backward; Enter executes; ↑/↓ or Ctrl+k/j browse history; Backspace edits; Esc cancels |
 | Search | Type a literal query; Enter accepts the current occurrence or finds the next match; ↑/↓ or Ctrl+k/j browse history; Backspace edits; Esc cancels |
 | Insert, Command, Search | Ctrl+u deletes backward to the logical line start |
 | Insert, Command, Search (macOS) | Option+Backspace deletes backward by word; Command+Backspace deletes backward to the logical line start |
@@ -194,7 +194,7 @@ Submitting an empty search repeats the last query. Esc cancels without moving th
 
 Up/Ctrl+k recalls older entries; Down/Ctrl+j recalls newer entries and restores the unfinished input after the newest. Navigation stops at either end without executing a command or moving search targets. Recalled text is editable without changing stored entries. Command and search histories are separate, shared across buffers/panes/tabs, and retained only for this editor session, up to 100 entries each. Enter records nonempty submissions, including unknown commands and searches with no matches; consecutive duplicates are skipped. Empty submissions and cancelled drafts are not recorded. Ctrl+j no longer submits Command/Search input; use Enter.
 
-Tab replaces the command-name prefix with the first case-sensitive match in alphabetical order; repeated presses cycle through the same matches and wrap. Candidates include canonical core commands, shorthand aliases, and commands from currently enabled plugins. Empty input cycles all command names. Typing, deleting, or browsing history starts a fresh completion cycle. Completion only changes the prompt: Enter still executes, and Escape cancels. Arguments (including paths) are not completed; Tab leaves them unchanged. Search-mode Tab remains literal text. Rebind or disable completion with `config.core.command_complete` in Command mode.
+Tab replaces the command-name prefix with the first case-sensitive match in alphabetical order; repeated presses cycle forward through the same matches and wrap. Shift+Tab cycles backward, starting at the last match when no cycle is active. Switching direction retains the original prefix. Candidates include canonical core commands, shorthand aliases, and commands from currently enabled plugins. Empty input cycles all command names. Typing, deleting, or browsing history starts a fresh completion cycle. Completion only changes the prompt: Enter still executes, and Escape cancels. Arguments (including paths) are not completed; Tab and Shift+Tab leave them unchanged. Search-mode Tab remains literal text. Rebind or disable forward/backward completion with `config.core.command_complete` / `config.core.command_complete_previous` in Command mode.
 
 Command input works in both Normal and Visual modes, including read-only diff panes. The original selection stays highlighted while typing. Enter dispatches with its ranges, direction, and linewise shape intact; individual commands decide whether to consume or retain them. Escape returns to the original Visual selection without executing. For example, select lines with `V`, then type `:diff.comment` and press Enter—no command palette is needed. `config.core.command` can also be bound in Visual mode.