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

templates/iso_a3_mech.dxf

@@ -489,7 +489,7 @@ $SKPOLY
   9
 $TDCREATE
  40
-2461306.528125
+2461308.9858101853
   9
 $TDUCREATE
  40
@@ -497,7 +497,7 @@ $TDUCREATE
   9
 $TDUPDATE
  40
-2461306.528125
+2461308.9858101853
   9
 $TDUUPDATE
  40
@@ -929,11 +929,11 @@ $PSTYLEMODE
   9
 $FINGERPRINTGUID
   2
-{522C5F29-75D3-427F-A718-E45B971550C2}
+{68192C9F-2E1B-4491-B3B5-24934A927E62}
   9
 $VERSIONGUID
   2
-{CF5A954B-3734-4AD2-B15E-F6411516FB5E}
+{B09ECF76-6F17-4166-8AA8-1673B93563F5}
   9
 $EXTNAMES
 290
@@ -2037,7 +2037,7 @@ Standard
  42
 2.5
   3
-txt
+arial.ttf
   4
 
   0
@@ -4541,7 +4541,7 @@ DictionaryVariables
 280
 0
   1
-1.4.4 @ 2026-09-22T09:40:30.742891+00:00
+1.4.4 @ 2026-09-24T20:39:34.680466+00:00
   0
 DICTIONARYVAR
   5
@@ -4553,7 +4553,7 @@ DictionaryVariables
 280
 0
   1
-1.4.4 @ 2026-09-22T09:40:30.898227+00:00
+1.4.4 @ 2026-09-24T20:39:34.829339+00:00
   0
 ENDSEC
   0