docs: convert all architecture .adoc sections to markdown, prettier-format all .md

- Converted 13 individual .adoc section files to .md via
  asciidoctor→docbook5→pandoc(gfm) + post-processing, placed alongside
  the .adoc sources in Docs/Architecture/
- Rebuilt architecture.md from the individual section .md files
- Ran prettier --write on all .md in the repo (23 files changed):
  normalised table column alignment, trailing whitespace, line breaks
- Added .agents/ to .prettierignore (vendored third-party content)
- All .md now passes prettier --check

Docs/Architecture/architecture.md

@@ -510,6 +510,14 @@ Rule: place a building only against a neighbour or street mesh, never in isolati
 
 **About arc42**
 
+<div data-wrapper="1" role="lead">
+
 arc42, the template for documentation of software and system architecture.
 
-Template Version 0.1.0. Adapted for the Gig Line project. Created, maintained and © by Dr. Peter Hruschka, Dr. Gernot Starke and contributors. See <https://arc42.org>.
+</div>
+
+Template Version 0.1.0. initial architecture documentation, 2026-11-08
+
+Created, maintained and © by Dr. Peter Hruschka, Dr. Gernot Starke and contributors. See <https://arc42.org>.
+
+Adapted for the Gig Line project (Linux-first walking/driving demo around 6840 Hollywood Blvd).