Vacuum controls: pick-up modes and separate pick-up and blow marks in the bag (t6, t15)

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

docs/DESIGN.md

@@ -43,7 +43,7 @@ decides something new, add it under "Decisions" with the date.
 ## The core loop
 
 1. Dig with the resonance drill. Rock shatters into loose grains: rubble, ore, coal, clay, sand.
-2. Vacuum up what you want (tick materials to take only those), and blow it out where you need it.
+2. Vacuum up what you want (mark materials with ⬇ to take only those), and blow it out where you need it.
 3. Build a furnace from wall blocks, with a grate floor over a mold. Charge it with ore and coal,
    light it, and let the molten metal run into the mold.
 4. Bars drop out of the bottom of the mold; collect them and sell them at the trade dock, or fill buyers' orders, which pay more.
@@ -127,8 +127,8 @@ above, including:
 - **Holding Ctrl** while placing replaces what is built there (moved to G on 2026-10-23).
 - **Fans melt like copper (1085°C).** Put the fan outside the furnace, blowing in through a grate.
   The game warns when a fan gets close to melting.
-- **The vacuum takes only ticked materials** when anything is ticked, even if the drag starts on
-  something else.
+- **The vacuum takes only marked materials** in Only marked mode, even if the drag starts on
+  something else. The t6 controls below replace the shared ticks.
 - **The Refiner** grinds stone, granite and basalt rubble, gravel, sand and dirt for trace ore,
   roughly halving the waste. Ore and anything else it cannot grind drop straight through.
 - **Pipes, pumps and outlets** move liquids up to 500°C, one liquid per line. A line is stored as
@@ -222,6 +222,9 @@ above, including:
 - **The bag is the vacuum's control panel (t6).** Each bag row has separate pick-up and blow
   marks; a chip on the tool card sets pick-up to everything, only marked, or the same as the
   first click; R over a grain toggles its pick-up mark. The owner found the shared ticks confusing.
+  As built: T or the chip cycles What I click → Only marked → Everything; adding a mark switches
+  to Only marked and removing the last goes back to What I click. A bag name or Q/E blows one
+  material; ⬆ marks build an even mix (bars are never mixed).
 
 ## Ideas not built yet