Add end-to-end process flow document and diagram; floor loading criterion

- docs/process-flow.md: mermaid chart plus stage table of every check and
  the three artist approval gates, from audio intake to fulfillment
- docs/process-flow.drawio with PNG and PDF exports
- pressing-line.md: floor must carry multiple tons per m2 in machine areas
- README: process-flow entry in document index and layout tree

README.md

@@ -78,6 +78,9 @@ The detail lives in dedicated documents:
   (Keyence-class confocal, profiler, XRF), layered pressed-record QC (100%
   optical inspection, per-cycle press telemetry, sampled automated audio
   comparison), and how it feeds traceability
+- [Process flow](docs/process-flow.md): the whole chain from audio file to
+  delivered record as a chart and stage table, with every check and the
+  three artist approval gates (printable diagram alongside)
 
 ## Repository Layout
 
@@ -91,6 +94,7 @@ docs/
 ├── finance/               Project cost overviews
 ├── suppliers/             Supplier contacts, vendor landscape, supplier map
 ├── facility-security.md   Security, HVAC, fire and life safety, compliance
+├── process-flow.md        Audio file to delivered record, with all checks
 ├── quality-automation.md  Stamper metrology and layered record QC
 ├── sustainability.md      Energy, water, materials commitments
 ├── traceability.md        Process logging and per-order traceability