Tabs: what does not fit goes behind a menu (#84)

Concepts gains the tab row; Architecture loses the 90 px floor, which is gone,
and names TabStrip/tabRow in the file tree. Counter 790.

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

Architecture.md

@@ -23,8 +23,12 @@
   measures from it — only what is drawn is shortened — and a subclass that puts something else
   inside the control takes its room off `labelSlot()`, so a long value is cut rather than run
   underneath the chevron. Given a `width`, a button is exactly that wide and truncates instead:
-  the Behavior, Texture, Animation and Container pickers keep their size whatever they show; the tab
-  bar uses 90 px as a floor. A button that can draw its label bold — on an accent fill: primary,
+  the Behavior, Texture, Animation and Container pickers keep their size whatever they show. The
+  tab row has no floor at all: it is label-wide at half the theme padding, and `TabStrip` drops
+  what does not fit into an overflow menu rather than letting it spill (the rule is
+  `tabRowLayout` in `editor/tabRow.ts`, so it is checkable without a browser; `__gm.tabRow()`
+  reports what is in the row and what went away).
+  A button that can draw its label bold — on an accent fill: primary,
   danger, a toggled tab — is measured bold, or a dialog's `Delete` comes out as `Del…`.
   The padding is an inset rather than a claim, so a 24 px icon button spends it on the glyph
   instead of truncating it away; a button that switches between label forms (`↺` and `↺ ▾`) asks
@@ -56,7 +60,8 @@ src/viewport/          view (transforms), items (what to draw), symbols (how to
 src/editor/            App → Editor (layout + ticker), PlaySession (the run), ProjectSession (load/create),
                        EditorRun (run in editor), state, actions, shortcuts, debugHook, autosave,
                        fileImport (drop/paste) → textureImport / fontImport,
-                       framing (fit/marquee/snap maths), AssetTabEditor (the shared shell of the asset tabs)
+                       framing (fit/marquee/snap maths), AssetTabEditor (the shared shell of the asset tabs),
+                       TabStrip + tabRow (the tab row and what it does when the tabs outgrow it)
 src/editor/viewport/   WorldViewport base + SceneViewport/GameViewport — editing tools, hence not in src/viewport/
 src/editor/inspector/  Inspector panel, host (what a section builds into), field factory, previewHandlers (scrub → preview → command), valueSpecs
                        (where a value lives — shared with the List tab),

Concepts.md

@@ -43,6 +43,13 @@ from texture* and *Delete…*. In
 **Scene objects** it offers *Select asset*, *Add collider*, *Create container*, *Unpack
 container*, *Unparent*, *Expand all* / *Collapse all* and *Remove*.
 
+**The tab row.** The centre column carries one button per tab. When the column is too narrow to
+hold them all — a small window, or the side panels dragged wide — the ones that do not fit move
+behind a `»` button at the end of the row, which lists them by name; picking one opens it and
+brings it into the row. The tab you are editing is always in the row: if it has to, the row gives
+up every other tab to keep it there. Nothing is ever drawn past the column's edge, where it would
+sit under the inspector and take clicks meant for it.
+
 **The console.** Under whichever centre tab is showing sits the **Console** panel, always
 visible and resized by the divider above it — dragged all the way shut it keeps its own header
 to be dragged open by. It mirrors everything that reaches the browser console: a `Log` node's

Development.md

@@ -12,7 +12,7 @@ npm run check        # typecheck + lint + format:check + tests, the gate CI runs
                      #   code is lost (tail's is reported), so a red run reads as green
 npm run build        # writes dist/ and regenerates index.html
 ./build.sh           # the same under `set -o pipefail`, for callers that pipe the output
-node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 785 editor checks, screenshots in /tmp/gm-e2e-*.png
+node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 790 editor checks, screenshots in /tmp/gm-e2e-*.png
 GM_STEPS=20 node tools/e2e.mjs                                # or 1-12, or 6,20 — a subset while working on one step
 ./e2e.sh start [GM_STEPS]                                     # the same run detached, see below
 ./e2e.sh status                                               # live progress, or the last run's result
@@ -151,4 +151,4 @@ widths to find click points. The **render device is not in this repo** — `/dev
 and a 1 GB `/dev/shm` come from `container.options` in the runner's own `config.yaml`, which
 applies to every job on that runner. Without them chromium falls back to llvmpipe, which gets
 WebGL 1.0 only. Measured in the job container: `ANGLE (Intel, Vulkan 1.3.230, HD Graphics 630)`,
-WebGL 2.0, and the same 785 checks as here.
+WebGL 2.0, and the same 790 checks as here.