Colour code with a scanner of our own instead of the library

dev.snipme:highlights 1.1.0 found comments before it knew the language and
paired /* with */ by ordinal, so `//` in any URL commented out the rest of
its line, every Rust `#[derive(...)]` greyed out as a comment, a `#` inside
a Kotlin string swallowed the line, and `x '*/a/*'` in shell produced a span
whose end preceded its start -- the one that crashed a card holding
`-path '*/.git/*'`. None of that could be post-processed away, because
comments won over strings before the language was known.

Highlighter.kt is one left-to-right scanner: at each position it is in a
line comment, a block comment, a string, or ordinary code, and every span is
emitted by advancing an index, so spans cannot overlap, arrive out of order
or run backwards. Languages.kt is a `Rules` row per language -- comment
tokens, block comment and whether it nests, the string forms, what opens an
attribute, and the keyword set -- so a new language is a table entry. The
keyword lists came from the library's SyntaxTokens.kt (Apache-2.0, noted at
the table) so nothing that is coloured today turns plain, and RON, TOML,
fish and JSON are coloured for the first time.

HighlighterTest.kt is a new JVM unit test source set -- 24 cases, the
library's mistakes kept as regressions, plus a sweep asserting no span
escapes the code for any language on unterminated and empty input.
AGENTS.md's app line now runs :androidApp:testDebugUnitTest.

Measured on the ai-app emulator, debug build, a ~200-line Kotlin fence sent
into a sandbox session:

  before  code highlighted: 1, 101.9ms total, 101.9ms mean, 101.9ms worst
  after   code highlighted: 1,  15.0ms total,  15.0ms mean,  15.0ms worst

and a second fence in the same run took 13.9ms, so that is the steady cost
rather than class loading. stream-bench.sh after the change:

  code highlighted: 1, 12.1ms total, 12.1ms mean, 12.1ms worst
  markdown reparsed while streaming: 1329, 2130.7ms total, 1.6ms mean, 8.7ms worst
  record: one block: 131, 11.4ms total, 0.1ms mean, 0.4ms worst
  draw phase 1.21ms per frame, the transcript 0.23ms of it

transcript-bench.sh after: draw phase 1.10ms per frame, the transcript
0.49ms (place 0.48), worst place 4.3ms -- unchanged within run-to-run noise,
as expected, since the scan happens in `warm` and not while drawing.

Looked at on the emulator: a URL inside a Kotlin string, a Rust attribute
with a lifetime and a raw string, a shell line with globs and `$#`, a RON
fence and a TOML fence all colour correctly; a Bash tool card still colours
its command; a plain Python fence -- which this change had no reason to
touch -- looks as it did; an unknown language stays plain; and a fence is
plain while it streams and colours when it freezes.

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

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

@@ -6,8 +6,6 @@ import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.darkColorScheme
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.graphics.Color
-import androidx.compose.ui.graphics.toArgb
-import dev.snipme.highlights.model.SyntaxTheme
 
 /**
  * Catppuccin Mocha, as published in `catppuccin/palette`.
@@ -198,24 +196,24 @@ val rawSurface: Color
     @Composable get() = Mocha.Crust
 
 /**
- * Catppuccin Mocha as a syntax theme, for the highlighter used on a tool call's input.
+ * Catppuccin Mocha as the highlighter's palette; see [SyntaxPalette].
  *
- * Here with the rest of the palette rather than beside the code that highlights: a library's own
- * theme would otherwise be the one surface in the app whose colours came from somewhere else, and
- * the accents below are the same ones every other coloured thing already uses.
+ * Here with the rest of the palette rather than beside the code that highlights: the colours a
+ * fence is drawn in are the same accents every other coloured thing in the app already uses, and
+ * splitting them out would make code the one surface whose palette came from somewhere else.
+ *
+ * Not a composable, because [highlight] runs off the drawing thread; these colours never vary with
+ * the theme.
  */
-fun catppuccinSyntax(): SyntaxTheme =
-    SyntaxTheme(
-        key = "catppuccin-mocha",
-        code = Mocha.Text.toArgb(),
-        keyword = Mocha.Mauve.toArgb(),
-        string = Mocha.Green.toArgb(),
-        literal = Mocha.Peach.toArgb(),
-        comment = Mocha.Overlay0.toArgb(),
-        metadata = Mocha.Yellow.toArgb(),
-        multilineComment = Mocha.Overlay0.toArgb(),
-        punctuation = Mocha.Subtext0.toArgb(),
-        mark = Mocha.Sky.toArgb(),
+fun catppuccinSyntax(): SyntaxPalette =
+    SyntaxPalette(
+        keyword = Mocha.Mauve,
+        string = Mocha.Green,
+        literal = Mocha.Peach,
+        comment = Mocha.Overlay0,
+        metadata = Mocha.Yellow,
+        punctuation = Mocha.Subtext0,
+        mark = Mocha.Sky,
     )
 
 /**