.ssp: omit empty-value array property entries

Add empty-string guards to array property loops
(.stow_link, .lev4_subtoc, .anchor_tag) so entries with
zero-length values are not emitted. Empty properties have
no value for PEG parsing - absent lines are faster to skip
than matching a property name to find an empty value.

Removes 1488 empty .anchor_tag: lines from Wealth of
Networks .ssp alone.

Co-Authored-By: Anthropic Claude Opus 4.6 (1M context)

1 files changed, 6 insertions, 3 deletions

diff --git a/src/sisudoc/io_out/create_abstraction_txt.d b/src/sisudoc/io_out/create_abstraction_txt.d
index d393f61..f92b83c 100644
--- a/src/sisudoc/io_out/create_abstraction_txt.d
+++ b/src/sisudoc/io_out/create_abstraction_txt.d
@@ -359,7 +359,8 @@ template spineAbstractionTxt() {
         /+ ↓ stow (extracted links) +/
         if (obj.stow.link.length > 0) {
           foreach (lnk; obj.stow.link) {
-            output ~= ".stow_link: " ~ lnk;
+            if (lnk.length > 0)
+              output ~= ".stow_link: " ~ lnk;
           }
         }
 
@@ -390,13 +391,15 @@ template spineAbstractionTxt() {
         /+ ↓ lev4 subtoc +/
         if (obj.tags.lev4_subtoc.length > 0) {
           foreach (st; obj.tags.lev4_subtoc) {
-            output ~= ".lev4_subtoc: " ~ st;
+            if (st.length > 0)
+              output ~= ".lev4_subtoc: " ~ st;
           }
         }
         /+ ↓ anchor tags +/
         if (obj.tags.anchor_tags.length > 0) {
           foreach (at; obj.tags.anchor_tags) {
-            output ~= ".anchor_tag: " ~ at;
+            if (at.length > 0)
+              output ~= ".anchor_tag: " ~ at;
           }
         }