docs(nook): mark split panes done in v0.51.0, note minimap foundation

Author: truffle-dev

cmd/nook/ROADMAP.md

@@ -29,7 +29,7 @@ These are load-bearing and do not bend for a feature.
   debug adapter client are all in-tree or shell out to tools the user
   already has (`gopls`, `git`, a DAP server).
 
-## Done (v0.50.0)
+## Done (v0.51.0)
 
 The editing core and most of the language-intelligence surface are in
 place. Grouped by area, each backed by a package under
@@ -39,7 +39,9 @@ place. Grouped by area, each backed by a package under
   highlight, comment toggling, indent guides, code folding, find and
   replace, register-based clipboard.
 - **Buffers & layout** — tab bar, buffer manager, multibuffer, file
-  tree with file operations, fuzzy finder, picker.
+  tree with file operations, fuzzy finder, picker, split panes
+  (horizontal and vertical, per-buffer sizing, `alt+w` window leader for
+  split/close/navigate/resize, click-to-focus).
 - **Language intelligence (LSP)** — hover, signature help with overload
   cycling, completion, code actions, rename, find-references, call
   hierarchy, inlay hints, document outline, symbol search, semantic
@@ -59,33 +61,27 @@ place. Grouped by area, each backed by a package under
 
 Roughly in priority order.
 
-1. **Split panes.** Horizontal and vertical view splits over the same or
-   different buffers. The single biggest layout gap against Zed. Has to
-   respect the first-paint rule and the recursive pump pattern used for
-   the existing panes. The geometry foundation is in place:
-   `internal/splitlayout` is a pure binary layout tree (leaf = pane,
-   internal = Columns/Rows split with a ratio) with split, close, ordered
-   and directional focus, divider-resize, rectangle computation, divider
-   line positions for rendering, and `PaneAt` hit-testing for mouse focus,
-   all constant-time and unit-tested. What remains is host wiring: rendering
-   each pane's editor view into its rect, drawing the dividers, routing
-   input to the focused pane, and the focus and split keybindings. The
-   wiring is decomposed into four green-shippable slices in
-   `docs/nook/design/01-split-panes-host-wiring.md`.
-2. **Full multi-cursor.** Add-cursor-at-next-match (ctrl+d),
+1. **Full multi-cursor.** Add-cursor-at-next-match (ctrl+d),
    select-all-occurrences (alt+d), stack-above/below (ctrl+↑/↓),
    split-selection-into-lines (alt+i), multi-line edit at every cursor,
    and consistent placement of the primary within its own match all
    work. What remains for a first class mode: column/box cursors (drag
    or keyboard column selection).
-3. **Vim mode.** Modal editing as an opt-in layer. Gated on an explicit
+2. **Vim mode.** Modal editing as an opt-in layer. Gated on an explicit
    product decision before build — it is a large surface and should not
    land half-done.
-4. **Tree-sitter highlighting.** Upgrade the syntax backend from chroma
+3. **Tree-sitter highlighting.** Upgrade the syntax backend from chroma
    to tree-sitter (via WASM) for incremental, error-tolerant parsing.
    chroma stays the fallback for grammars not yet wired.
-5. **Minimap.** Optional document overview gutter. Lowest priority of the
-   five; useful but not load-bearing for the editing experience.
+4. **Minimap.** Optional document overview gutter. Lowest priority;
+   useful but not load-bearing for the editing experience. The geometry
+   foundation is in place: `internal/minimap` is a pure, constant-time
+   `Model` that maps between source lines and minimap rows (`LineRange`,
+   `RowForLine`, `ViewportWindow` for the highlight band, `LineForRow`
+   for click-to-scroll), fully unit-tested, no I/O, inside the
+   first-paint rule. What remains is host wiring: rendering the column
+   from per-row buffer density, drawing the viewport band, and routing
+   click-to-scroll.
 
 ## How to pick the next slice