Add Connections to SSG_LIB, reusing the TRO mechanisms

A connection is a CONNECTION_ARROW block sitting at the midpoint of an arrow
between two TRO markers. It stores the relationship as attributes rather than by
position:

    TRO11  ---------->  TRO14
    UID 0062            UID 0065

Same architecture as the TRO feature, nothing new introduced:

  Blockname CONNECTION_*  ->  c:CONNECTION_EDIT (Lisp/Connection_Edit.lsp)
                          ->  dcl/connection_edit.dcl

The double-click and EATTEDIT hooks already route every INSERT through
SSG_BLOCKEDIT, so this is one more branch in that dispatcher - placed before the
TRO branch since both come from the same annotation run and the patterns must not
overlap. DCL path from DXFM_DCL, ssg-start/ssg-end, ssg-attrib-read and
ssg-attrib-set-on, all text via ssg-text/ssg-textf with 16 new keys in both
language files. Loading is lazy: not preloaded in the MNL, pulled by the menu
macros and the dispatcher with (ssg-ensure "Connection_Edit"), with a fallback to
native EATTEDIT if the module is missing.

CONNECTION_INSERT picks two TRO markers and draws the connection; the new
internal number comes from ssg-id-max/ssg-id-format, so it stays inside the
SSG_LIB number space. It refuses when the block definition is absent - the shape
comes from tro_annotate.py, this command does not invent one.

Menu: SSG_LIB > Connections with Verbindung einfuegen, Verbindung bearbeiten and
Bearbeiten (Auto), plus an entry in the POP501 edit context menu.

On the internal id: the markers keep their visible ID (TRO11) untouched - the
existing TRO_INSERT/tro-naechste-id read it and the request was explicit about
not changing it. The permanent unique number therefore lives in a separate
attribute UID, in the same four-digit space as ssg_id and the CSV TeileId.
Putting it into ID was tried and reverted: IDSCHECK treats ID as numeric and
would have overwritten TRO11 with a number while correcting duplicates.
Connections reference the UIDs, so the relationship survives a renamed or moved
marker.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Lisp/SSG_LIB_Commands.lsp

@@ -439,6 +439,23 @@
       (c:VARIOFOERDERER_EDIT)
     )
 
+    ;; Verbindungen (CONNECTION_*) -> CONNECTION_EDIT (DCL-Dialog)
+    ;; Vor der TRO-Pruefung, da beide aus der Beschriftung von sps_skel stammen
+    ;; und sich die Namensmuster nicht ueberschneiden duerfen.
+    ((wcmatch bname "CONNECTION_*")
+      (princ (ssg-textf "cmd-connection-bearbeiten" (list bname)))
+      (if (and (null *ssg-Connection_Edit-loaded*) (atoms-family 1 '("SSG-ENSURE")))
+        (ssg-ensure "Connection_Edit")
+      )
+      (if (atoms-family 1 '("C:CONNECTION_EDIT"))
+        (c:CONNECTION_EDIT)
+        (progn
+          (princ (ssg-textf "tro-edit-modul-fehlt" (list "Connection_Edit.lsp")))
+          (command "_.EATTEDIT")
+        )
+      )
+    )
+
     ;; TRO-Marker (TRO_SYM_<Typ>) -> TRO_EDIT (DCL-Dialog)
     ;; Die Marker kommen aus sps_skel (lib/tro_annotate.py) und tragen die
     ;; Attribute ID und TYPE. Modul bei Bedarf nachladen, damit der Doppelklick