bug: WritingSystems.Delete leaves the .ldml and an idchangelog Add entry behind #607

WritingSystemOperations.Delete (System/WritingSystemOperations.py ~:429-500) only removes the writing system from the vernacular and analysis lists. Its docstring says the writing system "is removed from both the store and active lists", but:

• WritingSystemStore/<tag>.ldml stays on disk, so ExistsInStore(tag) is still True afterwards;
• the <Add> entry for it in WritingSystemStore/idchangelog.xml stays.

Seen live on 2026-10-02 (Sena 3): Ensure('qaa-x-zzexcl', ...) created the writing system. Delete('qaa-x-zzexcl') removed it from the lists, but qaa-x-zzexcl.ldml and <Add Producer="???">...<Id>qaa-x-zzexcl</Id></Add> both remained, and had to be removed by hand.

Ask: remove (or move to trash/, as FieldWorks does) the .ldml, and record the delete in the change log the way FieldWorks does (it writes <Delete> entries). Or, at minimum, correct the docstring.

Related closed issues: #179 and #250 (Create / Exists).

Found during FlexToolsMCP specs/exclusive-access-gate (MattGyverLee/FlexToolsMCP#343); ledger: specs/exclusive-access-gate/issues/filing-ledger.md. Filing authorized by the maintainer on 2026-10-02.