feat: add configurable three-pane conflict views

docs/configuration.md

@@ -30,6 +30,7 @@ Vamp.configure do |config|
   config.diff_view_mode = "split" # or "unified"
   config.diff_split_orientation = "vertical" # or "horizontal"
   config.diff_follow_working_copy = true
+  config.resolve_history_layout = "columns" # or "base_below"
   config.review_directory = nil # XDG data directory; override with an absolute or config-relative path
   config.bind "ctrl+h", config.core.left, mode: config.modes.tree
   config.bind "ctrl+l", config.core.right, mode: config.modes.tree
@@ -104,6 +105,8 @@ Indicators compare the current editor text (including unsaved edits) against Git
 
 `config.diff_follow_working_copy` defaults to `true`. A Working-checkout After follows descendant checkouts automatically, including in inactive tabs; `false` disables endpoint following without disabling ordinary live-buffer editing or reload. Only literal booleans are accepted. Pinned After endpoints never move, but their checkout-aware editability checks remain enabled regardless of this setting. See [repository diff](editing.md#repository-diff) for ancestry and refresh behavior.
 
+`config.resolve_history_layout` controls the read-only conflict inputs opened by `:resolve.history`: `"columns"` (default) places left/base/right side by side; `"base_below"` places left/right above a full-width base. Both layouts share aligned rows and synchronized vertical scrolling. Tab/Shift+Tab follows layout order (left/base/right or left/right/base); directional pane actions follow the displayed geometry. Narrow terminals show the focused source only; the base-below layout does the same when there is insufficient height. This setting does not change the editable Resolution view or ordinary diffs. Invalid values reject the configuration.
+
 ```ruby
 config.bind "ctrl+b", config.core.diff.mode.toggle
 config.bind "leader v", config.core.diff.view.toggle