Draw a model's thinking as markdown

A model reasons in the same headings, lists and fenced code it answers in,
so plain text put rows of hashes and asterisks around the working the reader
opened the card to read. The card now draws `MarkdownText`, live while the
block is still open so a delta costs a parse of its last block rather than
of the whole reasoning, and the words answer the card's own tap through
`LocalMarkdownTap` the way a memory note's do.

A settled block is warmed with the rest of a page; an open one deliberately
is not, since warming a prefix per delta is a parse of the block per delta
held for ever. Echo's `/think` fixture is markdown now, because a fixture of
flat prose exercises none of this.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

app/androidApp/src/main/kotlin/com/example/aiapp/SessionScreen.kt

@@ -2024,6 +2024,7 @@ fun SessionScreen(
                                                 is TranscriptItem.ThinkingRow ->
                                                     ThinkingCard(
                                                         item = item,
+                                                        replies = replies,
                                                         expanded = item.seq in expandedThinking,
                                                         onToggle = {
                                                             toggleAnchored(