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

docs/development.md

@@ -71,6 +71,8 @@ Conflicted-revision regressions preserve unchanged symlinks, defer oversized uns
 
 Resolver checks use isolated real jj repositories: read-only discovery, marker-free all-side/base projections preserving outside edits and EOF, initial seed undo, hunk choice/undo, retained resolved files, jj-authoritative status, checkout/external-write refusal, cancellation, nontext bytes/types/modes/deletion, and directory-child protection. Render checks cover aligned gaps/highlights, context folding, native Draft focus/search/selection, separate History, hidden/on-demand explorer, viewport retention and narrow layouts. Live PTY smoke exercises frozen marker-free alternatives, History/Draft switching, hunk choice and guarded save confirmation without touching user repositories.
 
+Conflict History layout checks load `resolve_history_layout` through the real Ruby configuration and render both left/base/right columns and left/right over base. They cover source contents, full-width base geometry, Tab/directional focus, synchronized wheel scrolling, read-only base protection, narrow/short fallbacks and preserved Draft text. Live PTY smoke opens both layouts, focuses/scrolls the base, returns to Resolution, takes a hunk and saves; jj confirms the checkout is no longer conflicted.
+
 Shared-workspace parity checks compare ordinary and resolver diff geometry/content under identical chrome, focus and source cursors. Cover native picker selection/remaps, Tree/List and dock/floating actions, excerpt initialization, folded search, focus transfer on wheel, layout controls, loading/History/pane-rebuild transitions, and preserved per-file viewport state. Live PTY smoke uses Space e, Down/Enter file selection and guarded saving through the same explorer path.
 
 Repository gutter checks cover LF/CRLF normalization, additions/replacements/deletion anchors, staged/disk/unsaved Git text, unborn and missing named files, ignored/unsupported paths, read-only colocated/non-colocated jj queries, stale results and per-buffer isolation, plus rendered modes, colors, current-line precedence, wrap/scroll and narrow/split geometry. Live PTY smoke verifies all four modes, edit/undo refresh, external Git HEAD changes, and jj parent changes without editor restart.

docs/editing.md

@@ -536,7 +536,7 @@ Pane borders label the editable output **Resolution** and its frozen reference *
 | `resolve.history` / `resolve.view.toggle` | Show read-only input/base/input History / switch views |
 | `resolve.close` | Close the resolver without discarding dirty drafts |
 
-**History** is separate from editing: it compares the original inputs and their base, with all sides and bases selectable for multi-sided conflicts. Draft text, undo, caret and viewport survive view switches. Resolution uses the ordinary diff workspace, including its configured explorer, split/unified/orientation controls, source-line navigation, excerpts, focus and scrolling. Narrow History shows the focused input. Read-only Alternatives and History reject edits and saves.
+**History** is separate from editing: it compares the original inputs and their base, with all sides and bases selectable for multi-sided conflicts. `config.resolve_history_layout = "columns"` (default) shows left/base/right; `"base_below"` shows left/right above a full-width base. Both layouts retain aligned changes and synchronized vertical scrolling. Tab/Shift+Tab cycles in layout order; directional pane actions follow the displayed geometry. Narrow History shows the focused source, as does base-below History when too short to display both rows of panes. Draft text, undo, caret and viewport survive view switches. Resolution uses the ordinary diff workspace, including its configured explorer, split/unified/orientation controls, source-line navigation, excerpts, focus and scrolling. Read-only Alternatives and History reject edits and saves.
 
 Input indexes are one-based and include bases. Conflict-specific actions appear in the palette and through corresponding `config.core.resolve` methods. File navigation uses the existing picker/explorer actions: Space o opens floating search, Space e focuses the dock, Ctrl+t switches Tree/List, Ctrl+w closes it, and configured tree/selection bindings apply unchanged. Enter selects a relevant conflict file and focuses the editable Draft. Normal-mode Tab/Shift+Tab, native motions/search, context expansion and layout actions follow normal diff behavior. The complete seeded Draft can be saved even when intentional differences remain against the Alternative: those differences are not unresolved conflict markers. There is no automatic “accept both”.