Syntax highlighting improvements

- Fix cli-highlight import (use static import instead of dynamic require)
- Add syntax highlighting to read/write tool output
- Update dark/light themes with VS Code default syntax colors
- Add highlightCode and getLanguageFromPath exports
- Upgrade @google/genai to 1.34.0 for IMAGE_RECITATION/IMAGE_OTHER FinishReason
- Add AGENTS.md rule: never downgrade code to fix type errors from outdated deps

packages/coding-agent/src/modes/interactive/theme/dark.json

@@ -51,15 +51,15 @@
 		"toolDiffRemoved": "red",
 		"toolDiffContext": "gray",
 
-		"syntaxComment": "gray",
-		"syntaxKeyword": "cyan",
-		"syntaxFunction": "blue",
-		"syntaxVariable": "",
-		"syntaxString": "green",
-		"syntaxNumber": "yellow",
-		"syntaxType": "cyan",
-		"syntaxOperator": "",
-		"syntaxPunctuation": "gray",
+		"syntaxComment": "#6A9955",
+		"syntaxKeyword": "#569CD6",
+		"syntaxFunction": "#DCDCAA",
+		"syntaxVariable": "#9CDCFE",
+		"syntaxString": "#CE9178",
+		"syntaxNumber": "#B5CEA8",
+		"syntaxType": "#4EC9B0",
+		"syntaxOperator": "#D4D4D4",
+		"syntaxPunctuation": "#D4D4D4",
 
 		"thinkingOff": "darkGray",
 		"thinkingMinimal": "#6e6e6e",

packages/coding-agent/src/modes/interactive/theme/light.json

@@ -50,15 +50,15 @@
 		"toolDiffRemoved": "red",
 		"toolDiffContext": "mediumGray",
 
-		"syntaxComment": "mediumGray",
-		"syntaxKeyword": "teal",
-		"syntaxFunction": "blue",
-		"syntaxVariable": "",
-		"syntaxString": "green",
-		"syntaxNumber": "yellow",
-		"syntaxType": "teal",
-		"syntaxOperator": "",
-		"syntaxPunctuation": "mediumGray",
+		"syntaxComment": "#008000",
+		"syntaxKeyword": "#0000FF",
+		"syntaxFunction": "#795E26",
+		"syntaxVariable": "#001080",
+		"syntaxString": "#A31515",
+		"syntaxNumber": "#098658",
+		"syntaxType": "#267F99",
+		"syntaxOperator": "#000000",
+		"syntaxPunctuation": "#000000",
 
 		"thinkingOff": "lightGray",
 		"thinkingMinimal": "#9e9e9e",

packages/coding-agent/src/modes/interactive/theme/theme.ts

@@ -1,10 +1,10 @@
 import * as fs from "node:fs";
-import { createRequire } from "node:module";
 import * as path from "node:path";
 import type { EditorTheme, MarkdownTheme, SelectListTheme } from "@mariozechner/pi-tui";
 import { type Static, Type } from "@sinclair/typebox";
 import { TypeCompiler } from "@sinclair/typebox/compiler";
 import chalk from "chalk";
+import { highlight } from "cli-highlight";
 import { getCustomThemesDir, getThemesDir } from "../../../config.js";
 
 // ============================================================================
@@ -664,17 +664,94 @@ function getCliHighlightTheme(t: Theme): CliHighlightTheme {
 	return cachedCliHighlightTheme;
 }
 
-function requireCliHighlight(): { highlight: (code: string, opts?: any) => string } {
+/**
+ * Highlight code with syntax coloring based on file extension or language.
+ * Returns array of highlighted lines.
+ */
+export function highlightCode(code: string, lang?: string): string[] {
+	const opts = {
+		language: lang,
+		ignoreIllegals: true,
+		theme: getCliHighlightTheme(theme),
+	};
 	try {
-		const require = createRequire(import.meta.url);
-		return require("cli-highlight");
+		return highlight(code, opts).split("\n");
 	} catch {
-		return {
-			highlight: (code: string) => code,
-		};
+		return code.split("\n");
 	}
 }
 
+/**
+ * Get language identifier from file path extension.
+ */
+export function getLanguageFromPath(filePath: string): string | undefined {
+	const ext = filePath.split(".").pop()?.toLowerCase();
+	if (!ext) return undefined;
+
+	const extToLang: Record<string, string> = {
+		ts: "typescript",
+		tsx: "typescript",
+		js: "javascript",
+		jsx: "javascript",
+		mjs: "javascript",
+		cjs: "javascript",
+		py: "python",
+		rb: "ruby",
+		rs: "rust",
+		go: "go",
+		java: "java",
+		kt: "kotlin",
+		swift: "swift",
+		c: "c",
+		h: "c",
+		cpp: "cpp",
+		cc: "cpp",
+		cxx: "cpp",
+		hpp: "cpp",
+		cs: "csharp",
+		php: "php",
+		sh: "bash",
+		bash: "bash",
+		zsh: "bash",
+		fish: "fish",
+		ps1: "powershell",
+		sql: "sql",
+		html: "html",
+		htm: "html",
+		css: "css",
+		scss: "scss",
+		sass: "sass",
+		less: "less",
+		json: "json",
+		yaml: "yaml",
+		yml: "yaml",
+		toml: "toml",
+		xml: "xml",
+		md: "markdown",
+		markdown: "markdown",
+		dockerfile: "dockerfile",
+		makefile: "makefile",
+		cmake: "cmake",
+		lua: "lua",
+		perl: "perl",
+		r: "r",
+		scala: "scala",
+		clj: "clojure",
+		ex: "elixir",
+		exs: "elixir",
+		erl: "erlang",
+		hs: "haskell",
+		ml: "ocaml",
+		vim: "vim",
+		graphql: "graphql",
+		proto: "protobuf",
+		tf: "hcl",
+		hcl: "hcl",
+	};
+
+	return extToLang[ext];
+}
+
 export function getMarkdownTheme(): MarkdownTheme {
 	return {
 		heading: (text: string) => theme.fg("mdHeading", text),
@@ -692,8 +769,7 @@ export function getMarkdownTheme(): MarkdownTheme {
 		underline: (text: string) => theme.underline(text),
 		strikethrough: (text: string) => chalk.strikethrough(text),
 		highlightCode: (code: string, lang?: string): string[] => {
-			const { highlight } = requireCliHighlight();
-			const opts: any = {
+			const opts = {
 				language: lang,
 				ignoreIllegals: true,
 				theme: getCliHighlightTheme(theme),