Solar on every roof, BOI solar correction, open source section

Solar (user, 17 Oct 2026: "use as much roof space as possible")
- PV on every roof and canopy: ~640 kWp on the Payap scenario plot
  (factory roof ~523, canopies ~54, flat office roof ~65 kWp around the
  AC units); ~300 kWp on the Mueang Chi hall. Calculator: pvKWp 640,
  new pvSelf 85 % (zero export, hourly sketch), PV cost per kWp times the
  array, office-roof PV in the iso view, roofs drawn full.
- 12.8M to 16.6M THB at 20 to 26 THB/W; CSV baseline 34.37M to 56.34M;
  launch plant ~168M / 231M / 294M THB with contingency; Plan B ~216M
  (label ~215M), ~39M above Plan A; Plan A unchanged (it leases the
  array), its solar lever ~17.5M. PV payback ~4.2 to 5.9 years.
- Permits (rooftop solar no factory licence since 28 Dec 2024, ERC
  exemption under 1,000 kVA, PEA zero export) and PPA discounts sourced
  in sustainability.md.

BOI correction
- Announcement 3/2568 (in force 1 July 2025) ended BOI promotion for
  solar installations; only the battery may qualify (12M THB per MW cap).
  Removed the "BOI solar measure" from boi.md, total-investment,
  revenue-model, sustainability, site-candidates and both plan versions;
  Plan B's case for owning the array is the PPA bill it avoids
  (~0.07M USD a year).

Open source (user, 17 Oct 2026)
- digital-factory.md "Open source throughout, and working with other
  plants": everything we run and build is open source on NixOS, our code
  published (licence to decide), vendor firmware the stated exception;
  later the stack and factory-automation services for other pressing
  plants, not in the revenue.
- Business plan section 5.6 plus an executive-summary bullet, reading
  guide and not-modelled mentions; draft 0.3 rebuilt (A 60, B 61 pages),
  renders re-made with the roofs full.

docs/site-candidates.md

@@ -349,7 +349,16 @@ parameter does.
     shift), so PEA's export terms decide whether the surplus is sold or
     curtailed;
   - the 271 kWh battery is sized for ride-through, not to absorb it;
-  - the BOI solar measure caps eligible spend per MW ([BOI](boi.md)).
+  - the BOI no longer promotes solar installations (since 1 July 2025;
+    only the battery may qualify, [BOI](boi.md)).
+
+  Decided 17 October 2026: every roof and canopy carries PV. With the
+  flat office roof (~65 kWp around its AC units, estimate from the
+  [calculator](fleet-calculator.html) drawing) that is **~640 kWp**, the
+  size in the investment and the business plan. PEA's zero-export rule
+  answers the first point (surplus curtailed, ~85 % used on site in an
+  hourly sketch); the permits and the BOI position are in
+  [sustainability](sustainability.md#roof-design-for-pv-candidate-mueang-chi-site).
 
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 the cell (a normal recompute updates only the sheet). After editing