G-110: record tarjar .tclsocache precedent + c:/tclmodules/main preservation note

tarjar (modpod's tar-based predecessor) had a shared .tclsocache dll cache -
in-house prior art for the extraction-cache concept, though without content-hash
or collision handling; no code survives in current trees (grep-verified). Old
tarjar material at c:/tclmodules/main is preserve/partly-migrate, handled
manually by the user (explicitly not a goal) - tarjar artifacts are not
free-to-delete cruft.

Assisted-by: harness=claude; primary-model=claude-fable-5; api-location=anthropic.com

goals/G-110-sharedlib-extraction-cache.md

@@ -84,3 +84,12 @@ characterization of the existing behaviour), Tcl TIPs 741/709.
 
 - 2026-07-21: drafted and approved (user: "approved - apply both"); win32/
   old-Windows fallback requirement added from the approval message.
+- 2026-07-21 in-house precedent (user recollection): tarjar - modpod's
+  tar-archive-based predecessor - had a shared `.tclsocache` for dlls, though
+  without content-hash keying or copy-out collision handling. No `.tclsocache`
+  code survives in any current tree (verified by grep across the modpod project
+  and shellspy src), so it stands as prior art for the concept rather than
+  reusable code. Old tarjar material lives at c:/tclmodules/main - the user
+  intends to preserve and partly migrate it MANUALLY (explicitly not a goal);
+  tarjar artifacts elsewhere are not free-to-delete (see the modpod-tidy goal
+  when it lands).