Build menu: hover popup with full info, top-left card hidden while building

The short description row became a status row for the selected piece
(variant, Replace, ghosts, messages). Gamepad shows the selected tile's popup.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/DESIGN.md

@@ -146,7 +146,9 @@ above, including:
 - **Pick** (middle mouse) selects the piece under the cursor with its direction,
   wall material and filter settings. G is unbound, as the owner requested.
 - **The build menu** is a bar of tabs and icon tiles along the bottom: Structure, Moving,
-  Liquids, Machines, Molds. The owner wants more changes (see NOTES.md).
+  Liquids, Machines, Molds. Hover a tile for its full description, cost and placement help;
+  gamepad players see the selected tile’s popup. The top-left card is hidden while building,
+  with variants, ghosts and status kept in the bar so the world stays clear.
 - **No length limit when dragging.** Blocks out of the bot's reach become ghosts that it builds
   when it gets there.
 - **Pipes are thin:** sand, water and anything else loose passes them. Pumps and outlets are

docs/PROJECT_MAP.md

@@ -159,7 +159,7 @@ dist/, shots/         build output and screenshots (not committed)
 | Material properties and descriptions | `src/sim/materials.js` (`def`) |
 | Prices, orders, the dock | `src/sim/economy.js` |
 | Piece costs and descriptions | `src/sim/pieces.js` (`PIECES`) |
-| Build menu tabs, tiles and icons | `src/ui/build-menu.js` |
+| Build menu tabs, tiles, status and hover popup | `src/ui/build-menu.js` |
 | Key bindings | `src/ui/input.js` (keydown); what they do: `src/ui/actions.js` |
 | Mouse building and dragging | `src/ui/actions.js` (`primaryPress`, `primaryRelease`, `secondaryPress`, `toolTick`) |
 | Cursor previews (ghosts, drill aim, selection box) | `src/ui/previews.js` |
@@ -392,12 +392,12 @@ The notebook (N): milestones, market, wallet, blueprints, controls.
 The tool hotbar and what is selected.
 - functions: renderHotbar, toolId, steering, modShift, grainAt, selectTool, bagMaterials, mixList, ensureDropMat, piece
 
-### src/ui/build-menu.js (80 lines)
+### src/ui/build-menu.js (104 lines)
 The build menu along the bottom: categories, piece tiles and their icons.
 - functions: pieceIcon, catOf, selectBuildCat, cycleBuildCat, renderBuildBar, setupBuildBar
-- variables: BUILD_CATS, BUILD_ORDER, PIECE_ICONS, lastBuildKey
+- variables: BUILD_CATS, BUILD_ORDER, PIECE_ICONS, lastBuildKey, lastBuildMenu
 
-### src/ui/selection.js (246 lines)
+### src/ui/selection.js (228 lines)
 The selected tool and piece: R / Q / E, drill width, filter picker, the selection card, the bag panel.
 - functions: pieceUsesWall, setDrillWidth, tuneUnderCursor, cycleItem, cycleWall, rotate, toggleCollect, pickFilterUnderCursor, toggleFilterMat, toggleCollectUnderCursor, setBrush, pieceV, pieceExtra, filterChoices, matList, filterParts, filterSentence, applyFilterRun, openFilterPicker, filterBlockAt, chipCost, pieceCostNow, renderSelCard, renderBag
 - variables: lastBagKey

docs/agent-log.md

@@ -4,6 +4,27 @@ What agents have done, newest first. Add an entry for every piece of work: the d
 note or request it was for, what changed, the files touched, the tests run, and anything left
 open or not verified. Keep each entry short; the git history has the details.
 
+## 2026-10-23: build menu hover popup, top-left card hidden while building (Claude Code, with Codex)
+
+Notes: "mouse hover reviels a new info popup…" and "dont need the short description in the build
+menu…". The owner chose to hide the top-left card entirely while building.
+
+- `src/ui/build-menu.js`: `#bb-pop` above the hovered tile (icon, name, cost, size, power, full
+  description, how to place, filter help, build keys), clamped to the window; on a gamepad it
+  shows for the selected tile. The `.bb-tip` row became `.bb-status`: variant (material,
+  direction, filter) chips, Replace · Ctrl, ghosts waiting, and status messages. The bar now
+  updates its parts separately so hovering doesn't rebuild the tiles.
+- `src/ui/selection.js`: `#selcard` is hidden for the build tool unless copying, cutting or
+  pasting; the build branch moved to the bar. `src/styles/style.css`: popup and status styles;
+  on narrow screens the bottom-right panel moves up while building.
+- `src/ui/notebook.js`, `docs/DESIGN.md`, `docs/PROJECT_MAP.md`.
+- Tests: `play.py` 118 checks (popup on hover, switching tiles, hidden on leave, gamepad,
+  no `.bb-tip`, card hidden while building and back for tools 1 and 2, status in the bar; the
+  Ctrl replace check now reads the bar). All 11 headless suites pass. `t_smooth.py`'s
+  half-resolution check is still flaky under load (~4.8): 1 pass in 3 runs, as before.
+- Screenshots in `shots/` (build-popup-*) at 1280×800 and 900×700 in both looks.
+- Open: at 900px wide the bottom-left hover-info panel sits partly under the build bar.
+
 ## 2026-10-23: a backed-up heap on a belt no longer shears (Claude Code, with Codex)
 
 Note: "belts with a big pile on top only move the grains on the top of the stack…". The owner's