Field guide as a 10-page A4 PDF, one page per step

Rebuilt the guide as something usable on site rather than a document to read
at a desk: strict order of operations, DO / VERIFY / IF NOT blocks per step,
pass-fail gates in a table, a printable sign-off sheet, and troubleshooting
keyed by symptom rather than by subsystem.

Includes real screenshots of the add-on's own Web UI - captured by running it
against stub data - showing the healthy state and the misconfigured one side
by side, because telling those apart at a glance is the single most useful
skill on site. Plus the ESPHome step from a live builder.

The text lives only in docs/build_guide.py, which renders the HTML and drives
headless Chrome to produce the PDF. One source: a Markdown copy would
inevitably drift from the PDF someone is holding in a cellar.

Pagination is enforced, not hoped for. Each section must render under the A4
printable height (1039 px at 96 dpi) or Chrome silently spills it onto a second
page and the page numbers stop matching the step numbers. Measured every
section rather than eyeballing it: the Web UI reference page was 1170 px and is
now 1017 px, and the PDF comes out at exactly one page per section.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016NckgXecasQb2eSsPYNSW6

README.md

@@ -21,7 +21,9 @@ goodwe_controller/         the add-on
   DOCS.md                  the add-on's documentation tab
 firmware/goodwe-master.yaml  ESPHome config for the T-CAN485
 estop/rs485_log.py           optional RS485 e-stop / bus witness
-FIELD-GUIDE.md             installation, commissioning gates, troubleshooting
+docs/GoodWe-RS485-Field-Guide.pdf  the guide techs carry (10pp, A4)
+docs/build_guide.py          its single source - rebuilds the HTML and PDF
+FIELD-GUIDE.md             how to edit and rebuild the guide
 ```
 
 ## Install