fix(arch, table): what the 1.6.0 README renders showed

- The exterior dimension chains follow the plot scale. DIMSCALE is the
  plan's scale while they are drawn and is put back afterwards; a 1:50
  chain's 2.5 text had been 2.5 drawing units, 0.05 mm on the sheet.
- A headless TABLE merges its title row, as AutoCAD's TABLE does; a long
  title no longer wraps inside the first column over the header row.
- A headless TABLE's cell margin scales with the lettering. A flat 1.0 was
  0.02 mm on a 1:50 schedule; tables at the default 2.5 text are unchanged.
- drawing_new writes the Standard text style in arial.ttf, as AutoCAD
  2026's acadiso.dwt ships it: txt has no superscript two, so 'm²' read
  'm?' live and rendered as a box headlessly. The five bundled templates
  are rebuilt and build_templates --check reproduces them.

Each fix has a test that fails on the old code.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd

server.py

@@ -10090,8 +10090,9 @@ async def arch_dimension_chains(
     own faces, read back from the plan on the drawing. A row that would only
     restate a farther one is not drawn (ISO 129-1: each measurement once).
     The row spacing defaults (10 mm, then 8 mm on paper) are this server's
-    drafting choices, not standard values. Text height follows the current
-    dimension style: at 1:50 set DIMSCALE=50 with `dimstyle_modify`.
+    drafting choices, not standard values. Text, arrows and gaps follow the
+    plot scale: each chain is drawn at DIMSCALE = `scale` (reported as
+    `dimscale`), and the drawing's own DIMSCALE is put back afterwards.
 
     Refused by name: a drawing with no walls, an unknown or repeated side, a
     non-positive scale, offset or step.