fix(gemini3): remove RULES blank-line artifact

src/core/prompts/system-prompt/__tests__/__snapshots__/vertex_gemini3.tools.snap

@@ -151,7 +151,7 @@
       "properties": {
         "path": {
           "type": "STRING",
-          "description": "The path of the directory (relative to the current working directory {{CWD}}){{MULTI_ROOT_HINT}} to list top level source code definitions for."
+          "description": "The path of a directory (not a file) relative to the current working directory {{CWD}}{{MULTI_ROOT_HINT}}. Lists definitions across all source files in that directory. To inspect a single file, use read_file instead."
         },
         "task_progress": {
           "type": "STRING",

src/core/prompts/system-prompt/variants/gemini-3/overrides.ts

@@ -130,7 +130,7 @@ const GEMINI_3_RULES_TEMPLATE = (context: SystemPromptContext) => `RULES
 
 - The current working directory is \`{{CWD}}\` - this is the directory where all the tools will be executed from.
 - When executing terminal commands, new terminals always open in the workspace directory. Use relative paths or chain commands with proper shell operators (e.g., \`cd path && command\` to change directory and run a command together).
-- When executing commands, do not assume success when expected output is missing or incomplete. Treat the result as unverified and run follow-up checks (for example checking exit status, verifying files with \`test\` and \`ls\`, or validating content with \`grep\` and \`wc\`) before proceeding.${context.yoloModeToggled !== true ? " If output is still unavailable after reasonable checks and you need it to continue, use the ask_followup_question tool to request the user to copy and paste it back to you." : ""}
+- When executing commands, do not assume success when expected output is missing or incomplete. Treat the result as unverified and run follow-up checks (for example checking exit status, verifying files with \`test\` and \`ls\`, or validating content with \`grep\` and \`wc\`) before proceeding.${context.yoloModeToggled !== true ? " If output is still unavailable after reasonable checks and you need it to continue, use the ask_followup_question tool to request the user to copy and paste it back to you." : ""}${context.enableParallelToolCalling ? "\n- When multiple operations are independent (for example reading several files or searching in multiple directories), call multiple tools in a single response rather than one at a time. Use sequential tool calls only when later steps depend on earlier results." : ""}
 - When passing untrusted or variable text as positional command arguments, insert \`--\` before the positional values if they may begin with \`-\` (for example \`my-cli -- "$value"\`). This prevents the values from being parsed as options.
 - When searching, prefer the search_files tool over using grep in the terminal. If you are directly instructed to use grep, ensure your search patterns are targeted and not too vague to prevent extremely large outputs.
 - When using replace_in_file, pay careful attention to the EDITING FILES section above. The most common errors are: