Colour files by project in the Explorer, Open Editors and tabs

A fair question about the custom list: what does it buy over the built-in
Open Editors view? Most of the answer was the project colours — and those do
not need a custom view. A FileDecorationProvider puts them on the built-in
Open Editors view, the Explorer and the tabs, which keeps everything native
that view already does, including the drag-to-dock this list cannot offer.

verticalTabs.decorateFiles is off / color / colorAndBadge, defaulting to
color. Badges are the two characters a FileDecoration allows, taken from the
first and last segments of the project name so that Acme.Shop.Client and
Acme.Shop.Server read as AC and AS rather than colliding.

Two limits are documented rather than papered over: there is no way to
decorate only the Open Editors view, so the Explorer is coloured too; and Git
decorates modified files with only one colour winning, so a dirty file can
show Git's colour instead of its project's.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

README.md

@@ -5,6 +5,16 @@ off (`"workbench.editor.showTabs": "none"`), where a side list *is* the tab bar.
 
 It shows up as a **Tabs** view in the Explorer — drag it wherever you want it, including the secondary side bar.
 
+## Two ways to use it
+
+**Just the colours.**  colours files by project wherever VS Code shows file
+decorations — the Explorer, the built-in **Open Editors** view, and the editor tabs. If colour coding is all you
+want, use this and keep the built-in view: it drags to dock, shows file icons, and can focus every kind of tab.
+Set it to  to add a two-letter project badge such as  for .
+
+**The Tabs view.** A drawn list that the built-in view cannot be: a project border down each row, real spacing,
+and file names that keep their extension. Costs drag-and-drop and file icons — see *Known limitations*.
+
 ## What it adds over the built-in Open Editors view
 
 - **A colour per project**, as a border down the left of each row — the way Visual Studio marks them. The
@@ -37,6 +47,8 @@ the close button replaces on hover.
 
 ## Settings
 
+- `verticalTabs.decorateFiles` — colour files by project in the Explorer, Open Editors and tabs:
+  `off`, `color` (default), or `colorAndBadge`
 - `verticalTabs.order` — `open` (default), `project`, or `name`
 - `verticalTabs.pinnedFirst` — list pinned tabs above the rest (default `true`)
 - `verticalTabs.colorByProject` — colour each row's left border by project (default `true`)