Fix what the first Android run found

The flow ran on a Pixel 9a and its emulator (2026-10-02); what it found:

- The composer stayed on the card just written after "New flashcard", and
  on the original after "Duplicate": leaving a card changed the state
  before the new one was in it, so the screen took the new card for gone.
  It now waits for the card it asked for.
- Bottom sheets reached under the status bar with the keyboard open
  (useSafeArea).
- The field being written stayed behind the keyboard: the editor scrolls
  only within itself, so the card face now keeps it in view when it opens
  and when the keyboard rises, as a text field does.
- A tap on read-only rich text put a caret in it and opened the keyboard on
  phones, and in the composer never opened the field. RichContentView is
  display only now: no selection, taps go to what surrounds it, a sound's
  button still plays (decided 2026-10-02).
- The card types broke their names on a phone; they are choice chips that
  wrap (decided 2026-10-02).
- The week overview marked days before the person's first activity as
  missed; they show nothing now. An import starts the activity too, without
  counting as studying (decided 2026-10-02).
- A composer preview cut short gave no sign of it; it fades out over its
  last 32 dp, only when cut short (decided 2026-10-02).
- "Isn't on this device yet" showed for any image or sound that failed;
  a file that is here but can't be decoded now says so, and offers no retry.
- The signed-in account card was narrower than the anonymous one.
- The composer's title said "Create flashcards" also when opened on a
  stored card; it says "Edit flashcards in …" then (decided 2026-10-02).
- The Anki fixtures carry a valid PNG and a silent MP3, so they also serve
  to try the import by hand (decided 2026-10-02); regenerated with Anki
  26.9.3.

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

tool/anki/make_fixtures.py

@@ -35,12 +35,15 @@ from anki.decks import DeckId
 
 OUT = Path("halkyon_learn_flutter/test/feature/anki/fixtures")
 
-# A 1x1 PNG, and the start of an MP3 file: the import doesn't decode either.
+# Valid files, so the packages also serve to try the import by hand: a 1x1
+# PNG (one orange pixel), and 0.26 s of silence as an MP3 (ten MPEG-1 Layer
+# III frames, 128 kbit/s, 44.1 kHz, mono, whose zeroed side information
+# decodes to silence).
 PNG = bytes.fromhex(
-    "89504e470d0a1a0a0000000d4948445200000001000000010806000000"
-    "1f15c4890000000d49444154789c6360000002000154a24f5d0000000049454e44ae426082"
+    "89504e470d0a1a0a0000000d49484452000000010000000108060000001f15c489"
+    "0000000d49444154789c63f8dfc0f01f000680027f104c1be10000000049454e44ae426082"
 )
-MP3 = b"ID3" + bytes(200)
+MP3 = (bytes.fromhex("fffb90c4") + bytes(413)) * 10
 
 AGAIN, GOOD, EASY = 0, 2, 3