Add factory layout concept diagram and fix fire-suppression section structure

- docs/facility-layout.drawio: zoned floor concept (production, galvanics,
  utilities, logistics, support) with material and stamper flow arrows
- PNG and PDF exports alongside the source
- facility-security.md: suppression subsection no longer splits the fire
  safety bullet list; clean agent wording updated to FK-5-1-12

docs/facility-security.md

@@ -67,15 +67,46 @@ option per room.
 - **Fire detection and alarm** throughout; suppression matched to each zone
   (hot PVC and hydraulic oil in pressing, chemistry in galvanics, paper and
   cartons in packaging/finished goods, and the boiler room).
+
 - **Boiler room safety**: the steam generator (10 bar, 180 °C) needs its own
-  room, safety valves and interlocks, and inspection per Thai boiler
-  regulations (Department of Industrial Works requirements, licensed boiler
-  operator).
+  room, safety valves, fuel shutoff interlocks, and inspection per Thai
+  boiler regulations (Department of Industrial Works requirements, licensed
+  boiler operator).
 - **Emergency equipment in galvanics**: eyewash stations and emergency
   shower at the plating line, spill kits, and neutralizing agents.
 - **Emergency lighting, marked exits, assembly point**, and first-aid
   coverage on every shift.
 
+### Suppression design position: zoned, not full-building gas
+
+A full-building gas suppression system is ruled out: gas agents only work in
+sealed volumes that can hold concentration, which a ventilated production
+hall with people and loading doors cannot, and CO2 flooding is lethal in
+occupied spaces. The design position is zoned suppression:
+
+- **Clean agent gas** (FK-5-1-12, sold as Novec 1230, or inert gas such as
+  IG-541) only in small, sealed, high-value rooms: the server/IT room,
+  electrical switchrooms, PLC/control cabinets (in-cabinet micro systems),
+  and above all the master/stamper archive, where sprinkler water would
+  destroy lacquers and paper records and corrode the metal parts even in a
+  minor event.
+- **Water** (sprinklers, or water mist where equipment matters) for the
+  large spaces: production, warehouse, and packaging/finished goods, where
+  paper cartons are the largest fire load in the building. The press hall's
+  specific risk is a hydraulic oil spray fire (200 L at 180 bar); water
+  mist handles oil fires well and is gentler on machines than deluge.
+- **Battery stack (BESS)**: gas does not stop lithium thermal runaway. Per
+  NFPA 855 practice the stack needs off-gas and early-smoke detection,
+  electrical isolation on alarm, physical separation from production
+  (ideally its own enclosure), and deflagration venting. Detection and
+  containment over suppression.
+- **Galvanics**: low fire load (aqueous baths); local clean-agent
+  protection for rectifier cabinets is sufficient.
+
+The property insurer will drive much of the final specification, so involve
+them before the design is fixed. The archive gas system and the BESS
+detection affect room layout and belong in the site design brief early.
+
 ## Plant systems and monitoring
 
 - **Utility monitoring and interlocks**: fume-extraction interlocks on the