Colour list markers by depth, highlight fences, draw images as links, and stream a list an item at a time

Items 1-5 of TRANSCRIPT_RENDERING.md's list, plus the AGP 9.4.0 bump from 7.
MarkdownRoot provides the renderer's locals itself instead of calling its
Markdown() composable; fences and indented blocks go through CodeFence.kt,
which shares the tool-input highlighter and a fence-language alias table;
an image in a paragraph is a link carrying its alt text, so every paragraph
is now platform text; LiveParse freezes the finished items of the tail list
so a forty-item list streams as forty paragraphs would.

Measured before, on the emulator (report from transcript-bench.sh over the
200-line fence fixture): draw phase 0.72ms per frame, transcript 0.36ms.
stream-bench.sh (new) streaming forty linked bullets on the old build:
markdown reparsed while streaming 483, 3.9ms mean, 11.6ms worst; record:
one block worst 1.6ms. The after runs, the on-screen check of the glyphs
and lint are recorded as owed in the doc's "What is next".

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

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

@@ -16,7 +16,6 @@ import androidx.compose.ui.semantics.semantics
 import androidx.compose.ui.text.TextStyle
 import androidx.compose.ui.unit.Dp
 import androidx.compose.ui.unit.dp
-import com.mikepenz.markdown.compose.LocalMarkdownColors
 import com.mikepenz.markdown.compose.LocalMarkdownComponents
 import com.mikepenz.markdown.compose.LocalMarkdownPadding
 import com.mikepenz.markdown.compose.LocalMarkdownTypography
@@ -98,9 +97,20 @@ val BLOCK_SPACING: Dp = 6.dp
  * or heading is a [LinkedText], a table is [LinkedTableRow]s, and a nested list comes back here
  * through [MarkdownList]. Only the list item is drawn directly, because a list item is the one
  * piece the renderer has no element for.
+ *
+ * [continuesList] and [listContinues] are for a list cut across the segments of a live reply (see
+ * `LiveParse`): an item that is the first or last of its own parse but not of the list the reader
+ * sees keeps an inner item's padding, so nothing moves when the seam between segments does.
  */
 @Composable
-fun MarkdownPiece(parse: State, text: String, piece: Piece, modifier: Modifier = Modifier) {
+fun MarkdownPiece(
+    parse: State,
+    text: String,
+    piece: Piece,
+    modifier: Modifier = Modifier,
+    continuesList: Boolean = false,
+    listContinues: Boolean = false,
+) {
     if (parse !is State.Success) {
         // The parser threw. Nothing else in the app has seen this happen; if it does, the words
         // are still worth more than a blank.
@@ -124,8 +134,8 @@ fun MarkdownPiece(parse: State, text: String, piece: Piece, modifier: Modifier =
             list = node,
             item = items[piece.item],
             index = piece.item,
-            first = piece.item == 0,
-            last = piece.item == items.lastIndex,
+            first = piece.item == 0 && !continuesList,
+            last = piece.item == items.lastIndex && !listContinues,
             depth = 0,
             modifier = modifier,
         )
@@ -195,7 +205,7 @@ private fun MarkdownListItem(
         } else if (list.type == MarkdownElementTypes.ORDERED_LIST) {
             Marker("${list.startNumber(content) + index}. ", typography.ordered)
         } else {
-            Marker("• ", typography.bullet)
+            Marker(BULLETS[depth % BULLETS.size], typography.bullet)
         }
         Column {
             item.children.forEach { child ->
@@ -212,16 +222,24 @@ private fun MarkdownListItem(
     }
 }
 
-/** The renderer's text colour on the marker; its styles carry none of their own. */
+/** The marker in [listMarkerColor]; the renderer's styles carry no colour of their own. */
 @Composable
 private fun Marker(text: String, style: TextStyle) {
-    BasicText(text, style = style.copy(color = LocalMarkdownColors.current.text))
+    BasicText(text, style = style.copy(color = listMarkerColor))
 }
 
-private val ASTNode.isList: Boolean
+/**
+ * The bullet at each depth, cycling past the third: a disc, a ring, a square -- the ladder a
+ * browser draws, so a nested list is told from its parent by the glyph as well as by the indent.
+ * Checked on the emulator's system fonts, which is what makes them safe to rely on; a glyph the
+ * platform lacks draws as a box, and that check is the price of adding one here.
+ */
+private val BULLETS = listOf("• ", "◦ ", "▪ ")
+
+internal val ASTNode.isList: Boolean
     get() = type == MarkdownElementTypes.ORDERED_LIST || type == MarkdownElementTypes.UNORDERED_LIST
 
-private fun ASTNode.listItems(): List<ASTNode> = children.filter {
+internal fun ASTNode.listItems(): List<ASTNode> = children.filter {
     it.type == MarkdownElementTypes.LIST_ITEM
 }