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/gradle/libs.versions.toml

@@ -2,7 +2,8 @@
 # Maven Central; prereleases deliberately skipped). zxing-embedded checked
 # 2026-08-25.
 [versions]
-agp = "9.3.2"
+# Checked 2026-09-03 against Google Maven; 9.5.0 was alpha only.
+agp = "9.4.0"
 kotlin = "2.4.10"
 compose-multiplatform = "1.12.0"
 # material3 ships on its own release train, separate from the CMP version.