feat(learn): Add material no longer offers flashcards from a text (ADR 0021, D56 amended)

The developer's review of 4 Nov 2026. The entry goes from a studyset's
Add material, and with it the sheet for pasting a text
(proposeCardsFromText, _TextSheet), its three texts and proposeCards'
fromStudyset, which only it set to false. A note's and a PDF page's
flashcards stay; their tests now drive the proposals sheet from a note.

Whats-New: Add material no longer offers Flashcards from a text; a note's or a PDF page's flashcards stay.
Whats-New-De: Material hinzufügen bietet keine Karteikarten aus einem Text mehr an; die aus einer Notiz oder einer PDF-Seite bleiben.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

docs/adr/0021-private-instance-and-assistant.md

@@ -364,7 +364,9 @@ On 26 Oct, how the third step is built (the assistant answering in Learn):
   Add material › Flashcards from a text (a paragraph pasted or typed). Amended 26 Oct, as
   built: a note's text selected is left for later, as the note editor's selection can't
   be reached from its app bar as the PDF reader's is; and the entry is named for what it
-  makes, as the other Add material entries are, not "With an assistant".
+  makes, as the other Add material entries are, not "With an assistant". Amended 4 Nov
+  2026 (the developer's review): Flashcards from a text goes from Add material, and with
+  it the sheet for pasting a text; a note's and a PDF page's stay.
 
 On 26 Oct, after the first use on learn.halkyon.eu (the developer: granting three people
 all models of two providers would take dozens of sheets; a list of hundreds waiting would