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

Geo/manifests/2026-11-06-3dep-dem.md

@@ -22,7 +22,7 @@ The window is the block plus a ~100 m margin on the east and ~70 m on the other
 The raster is reprojected by the service, not by us, so it was checked against the service's own point query (`getSamples`) and against the independent point service used in `../verification/2026-11-06-elevation.md`:
 
 | Point | Raster pixel | Service `getSamples` | Earlier point probe |
-| --- | ---: | ---: | ---: |
+| --- | --: | --: | --: |
 | Hollywood × Highland (origin) | 115.911 | 115.910 | 115.911 |
 | Hollywood × Orange Dr | 119.422 | 119.418 | 119.418 |
 | Mid-block crossing | 117.593 | — | 117.53 |