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- Add AGENTS.md rule: never downgrade code to fix type errors from outdated deps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/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",