feat: reuse the docked file tree for diff navigation

docs/architecture.md

@@ -10,7 +10,7 @@ One crate; no workspace or terminal-coordinate types in the editing backend:
 
 - `editor`: owns buffer lifecycle and per-buffer text, saved state, primary/selection set, modes, search, and undo/redo; session-wide clipboard policy, independent registers and owned-system fragment metadata, semantic native repeat, action metadata, command-palette and file-picker focus/dispatch, key notation, leader/count prefixes and binding resolution, modal paste policy, saving, command ownership, capabilities, and validated edit effects. Its low-level interface returns an `Invocation` when an external command is selected.
 - `files`: owns the gitignore-aware directory/file catalog, authoritative OS paths, compact tree projection, query filtering, browse/search focus, expansion/selection restoration, navigation, and scan/error state shared by floating and docked presentations.
-- `diff`: owns searchable Before/After selection, category and focus state, request freshness, read-only comparison DTOs, and aligned rows/shared vertical and independent horizontal offsets. It has no subprocess or terminal dependencies.
+- `diff`: owns searchable Before/After selection, category and focus state, request freshness, read-only comparison DTOs, and aligned rows/shared vertical and independent horizontal offsets. Changed paths form a virtual `files::FilePicker` catalog, reusing the normal tree projection, filtering, and navigation without scanning disk. It has no subprocess or terminal dependencies.
 - `repository`: discovers jj/Git repositories and local/advertised remote revisions, builds disk snapshots and changed-file hunks, and owns isolated temporary comparison repositories with bounded, cancellable subprocesses. It never saves editor buffers or modifies active refs/checkouts.
 - `clipboard`: owns native plain-text provider selection and bounded subprocess I/O; it never computes selections or editing offsets.
 - `syntax`: owns Tree-sitter grammar detection, per-buffer incremental trees, bundled highlight/local/injection queries, and syntax byte spans; it has no terminal color/geometry or editing dependency.

docs/configuration.md

@@ -135,6 +135,8 @@ config.bind "ctrl+f", config.core.right, mode: config.modes.tree
 config.bind "ctrl+h", nil, mode: config.modes.tree
 ```
 
+The diff's right-docked changed-file explorer uses these same tree and selection contexts, including remaps and disabled keys. Enter opens the selected file's diff rather than an editable buffer; its catalog comes from the comparison, not a disk scan.
+
 Ctrl+h is **not** a Backspace alias or default deletion key in any mode. Raw Ctrl+h (0x08) and Backspace (DEL/0x7f) are distinct, as are CSI-u events. In the tree it navigates in NORMAL and INSERT without deleting query text; it never deletes file-buffer Insert text by default. Explicit `config.core.backspace` bindings remain available if desired.
 
 Ctrl+j is distinct from Enter: in the TUI's raw mode, LF is Ctrl+j and CR is Enter; CSI-u control events also work. No enhanced-terminal negotiation is required. Ctrl+m remains an Enter alias. Outside completion and selection lists, Ctrl+k still clones above in Normal/Visual, and Ctrl+j defaults to newline in Insert or submit in Command/Search. While completion is open, Ctrl+j/k cycles candidates; Enter always closes completion and inserts a newline. Enter and Ctrl+j can be rebound independently outside the completion cycle.

docs/development.md

@@ -47,6 +47,8 @@ Clipboard checks use isolated providers rather than reading or overwriting the d
 
 Diff checks cover staged category/filter navigation, stale request cancellation, row alignment, read-only buffer isolation, and rendered panes. Repository integration fixtures exercise Git and Git-backed jj, advertised but unfetched remote branches/bookmarks/tags, imported historical commit/change IDs, conflicts, unusual paths, binary/mode/link/submodule changes, and unchanged active metadata. Remote fixtures are local bare copies; they never push. Git fixture identities and commit dates are fixed.
 
+Changed-file explorer checks cover reuse of the compact directory tree, removed/historical paths, file-to-directory transitions, remapped tree/selection bindings, filter/open/focus transitions, right-dock geometry, and wheel routing without edits to the underlying document.
+
 ## Performance and process limits
 
 - Undo uses full-buffer snapshots and movement scans the current line. This favors straightforward correctness over large-file performance.

docs/editing.md

@@ -209,7 +209,9 @@ The floating selector has **Revisions / Bookmarks** tabs for jj, or **Commits /
 
 Remote references such as `some-bookmark@origin` appear from remote advertisements, including refs never fetched locally. Selecting one retrieves missing content into a temporary comparison repository. **Load history from origin** (or another configured remote) in Revisions/Commits imports searchable remote history without advancing the selection stage. These operations may require network access and the repository's existing credentials; errors stay in the selector. They do not update active refs, snapshot jj's working copy, or change the checkout.
 
-The read-only comparison has a changed-file navigator, Before on the left, and After on the right. Added/deleted rows are aligned with blank counterparts. Tab/Shift+Tab cycles focus between Files, Before, and After. Up/Down or Ctrl+j/k selects files or scrolls both text panes together; Left/Right or Ctrl+h/l scrolls the focused text pane horizontally. Home/End goes to the first/last file or aligned row. Wheel input over a text pane scrolls both panes; over Files it navigates changed files. Esc closes and preserves the editor's buffers, cursors, unsaved text, and undo history. Typing and pasted text cannot edit either snapshot.
+The read-only comparison has Before on the left, After on the right, and the changed-file explorer **docked on the right**. The explorer reuses the normal compact directory tree, filtering, and configurable `tree`/`selection` navigation. Its catalog contains only changed paths, including removed and historical files; it does not scan the working directory. Use h/j/k/l or control/arrow navigation, Enter to toggle a folder or open a file, `i` to filter, Ctrl+u to clear, and Ctrl+t to switch Tree/List. Opening a file focuses Before.
+
+Added/deleted rows are aligned with blank counterparts. Tab/Shift+Tab cycles focus between Files, Before, and After. In text panes, Up/Down or Ctrl+j/k scrolls both panes together; Left/Right or Ctrl+h/l scrolls the focused pane horizontally. Home/End goes to the first/last tree row or aligned text row. Wheel input over a text pane scrolls both panes; over Files it navigates visible tree rows without opening them. Esc first leaves filtering when the tree is focused; otherwise it closes the diff and preserves the editor's buffers, cursors, unsaved text, and undo history. Typing and pasted text cannot edit either snapshot.
 
 Binary data, missing final newlines, permission/type changes, symlink targets, and submodule pointers have explicit notices. Symlinks are not followed and submodule contents are not traversed. jj conflicts use jj's file-content projection and carry conflict notices; ordinary files remain readable. Identical-content moves are shown as renames; modified moves appear as an added and removed file.