Plan the overhead crane, maintenance workshop and visitor corridor

New docs/crane-workshop-tours.md: a 5 t single-girder EOT crane over the
whole production compartment (stops at the warehouse fire wall), a
machine door and crane-served workshop/machine bay at the ramp end, and
a glazed ground-level visitor corridor along the car-park elevation with
stations in process order, its own air and acoustic glazing so tours
need no PPE. Covers what each changes in the shell (crane-ready frame,
hook height under the 7.0 m eave, no full-height cross walls in the
crane zone, room lids and crane hatches), safety, costs and open
decisions.

Propagated: construction RFQ (crane-ready frame, new section 1c, machine
door, accessible 1:12 entrance now required), scale zone table (+210 to
280 m2, total ~1,400 to 2,000 m2), facility security, worker safety,
roadmap items 9 and 15, total investment added-scope table, README.

README.md

@@ -85,6 +85,12 @@ The detail lives in dedicated documents:
   control, CCTV, whole-factory HVAC (temperature, humidity, PM), archive and
   audio protection, fire and life safety, plant monitoring, Thai compliance
   anchors
+- [Overhead crane, workshop and visitor corridor](docs/crane-workshop-tours.md):
+  a 5 t crane over the whole production floor to move machines in and
+  out, a crane-served maintenance workshop and machine bay at the ramp
+  end, and a glazed ground-level corridor for guided tours without noise,
+  dust or plating chemistry; what each changes in the building and what
+  it costs
 - [Process logging and traceability](docs/traceability.md): end-to-end
   per-order traceability for customers, batch genealogy from audio file to
   shipment, and the requirements this sets for the factory software
@@ -151,6 +157,7 @@ docs/
 ├── suppliers/             Supplier contacts, vendor landscape, supplier map
 ├── biomass.md             Biomass fuel strategy and the 60 rai coppice idea
 ├── boi.md                 BOI promotion strategy and requirements
+├── crane-workshop-tours.md Overhead crane, workshop, visitor corridor
 ├── digital-factory.md     Data platform, NixOS/Clan fleet, acquisition, app
 ├── facility-security.md   Security, HVAC, fire and life safety, compliance
 ├── process-flow.md        Audio file to delivered record, with all checks