🤖 refactor: make file edit tool warnings more prominent (#502)

## Problem

Agents assume file edits succeed and proceed with dependent operations
(commits, pushes, builds) before tool results return. During streaming,
the agent generates optimistic text like "Now I'll push..." before edit
results arrive. When asked later, the agent knows about the failure
(it's in context), but the damage is done.

## Solution

Move the critical warning to the **first line** of all file edit tool
descriptions with a ⚠️ emoji:

```
⚠️ CRITICAL: Always check tool results - edits WILL fail if old_string is not found or unique. 
Do not proceed with dependent operations (commits, pushes, builds) until confirming success.
```

Applied to:
- `file_edit_replace_string`
- `file_edit_replace_lines`
- `file_edit_insert`

## Why This Helps

Warnings buried mid-description are easy for streaming models to miss.
By placing the warning **first** with a visual indicator, we increase
the likelihood that agents will:

1. Pause before assuming success
2. Check tool results explicitly
3. Only proceed with dependent operations after confirmation

_Generated with `cmux`_

Author: ammar-agent

src/utils/tools/toolDefinitions.ts

@@ -70,8 +70,8 @@ export const TOOL_DEFINITIONS = {
   },
   file_edit_replace_string: {
     description:
-      "Apply one or more edits to a file by replacing exact text matches. All edits are applied sequentially. Each old_string must be unique in the file unless replace_count > 1 or replace_count is -1. " +
-      `IMPORTANT: Edits may fail if old_string is not found or not unique. ${TOOL_EDIT_WARNING}`,
+      "⚠️ CRITICAL: Always check tool results - edits WILL fail if old_string is not found or unique. Do not proceed with dependent operations (commits, pushes, builds) until confirming success.\n\n" +
+      "Apply one or more edits to a file by replacing exact text matches. All edits are applied sequentially. Each old_string must be unique in the file unless replace_count > 1 or replace_count is -1.",
     schema: z.object({
       file_path: z.string().describe("The absolute path to the file to edit"),
       old_string: z
@@ -91,8 +91,8 @@ export const TOOL_DEFINITIONS = {
   },
   file_edit_replace_lines: {
     description:
-      "Replace a range of lines in a file. Use this for line-based edits when you know the exact line numbers to modify. " +
-      `IMPORTANT: Edits may fail if line numbers are invalid or file content has changed. ${TOOL_EDIT_WARNING}`,
+      "⚠️ CRITICAL: Always check tool results - edits WILL fail if line numbers are invalid or file content has changed. Do not proceed with dependent operations (commits, pushes, builds) until confirming success.\n\n" +
+      "Replace a range of lines in a file. Use this for line-based edits when you know the exact line numbers to modify.",
     schema: z.object({
       file_path: z.string().describe("The absolute path to the file to edit"),
       start_line: z.number().int().min(1).describe("1-indexed start line (inclusive) to replace"),