feat: System Message tools

[RomneyDa]

A remake of #5809 and #6395

Adds support for tools in the form of system message instructions and response content parsing + tests
Tools are parsed as they come in, converted to ToolCalls, and on the way out converted back to text. Switching between native and non-native tools is interchangeable with this approach.
For now, this applies only to models that are NOT known to support native tools
Adds a warning to the Agent mode dropdown that shows for any models not known to be great with tools (including models that support native tools)
All models can now be used in Agent mode

---

Summary by cubic

Added support for using tools via system message instructions and response parsing for models that do not natively support tools. All models can now use Agent mode, with a warning shown for models not recommended for tool use.

• New Features
  • Tools are now parsed from and converted to system message text for non-native tool models.
  • Added an experimental setting to force system message tool usage.
  • Agent mode is available for all models, with a warning in the UI for models not recommended for tools.
  • Tests and utility functions for system message tool parsing and formatting.

[cubic-dev-ai]

cubic analysis

2 issues found across 24 files • Review in cubic

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[sestinj]

This was the output in the continue Console, but chat window didn't seem to parse the whole thing. This is with Claude Sonnet 4, and it reproduces seemingly every time with "remove the comments from test.js"

Now I'll remove all the comments from the test.js file, including JSDoc comments, inline comments, and TODO comments.

```tool
TOOL_NAME: search_and_replace_in_file
BEGIN_ARG: filepath
test.js
END_ARG
BEGIN_ARG: diff
[
"------- SEARCH
/**
 * A calculator class that supports method chaining for basic arithmetic operations.
 * Maintains an internal result state that can be modified through various operations.
 */
class Calculator {
  /**
   * Initialize the calculator with a result value of 0.
   */
  constructor() {
    this.result = 0;
  }

  /**
   * Add a number to the current result.
   * @param {number} number - The number to add
   * @returns {Calculator} Returns this instance for method chaining
   */
  add(number) {
    this.result += number;
    return this;
  }

  /**
   * Subtract a number from the current result.
   * Note: This method appears to be incomplete - it doesn't perform the subtraction.
   * @param {number} number - The number to subtract
   * @returns {Calculator} Returns this instance for method chaining
   */
  subtract(number) {
    // TODO: Implement subtraction logic
    // this.result -= number;
    return this;
  }

  /**
   * Multiply the current result by a number.
   * @param {number} number - The number to multiply by
   * @returns {Calculator} Returns this instance for method chaining
   */
  multiply(number) {
    this.result *= number;
    return this;
  }

  /**
   * Divide the current result by a number.
   * @param {number} number - The number to divide by
   * @returns {Calculator} Returns this instance for method chaining
   * @throws {Error} Throws an error if attempting to divide by zero
   */
  divide(number) {
    // Prevent division by zero
    if (number === 0) {
      throw new Error("Cannot divide by zero");
    }
    this.result /= number;
    return this;
  }

  /**
   * Get the current result value.
   * @
assistant
returns {number} The current result
   */
  getResult() {
    return this.result;
  }

  /**
   * Reset the calculator result back to 0.
   * @returns {Calculator} Returns this instance for method chaining
   */
  reset() {
    this.result = 0;
    return this;
  }
}
=======
class Calculator {
  constructor() {
    this.result = 0;
  }

  add(number) {
    this.result += number;
    return this;
  }

  subtract(number) {
    return this;
  }

  multiply(number) {
    this.result *= number;
    return this;
  }

  divide(number) {
    if (number === 0) {
      throw new Error("Cannot divide by zero");
    }
    this.result /= number;
    return this;
  }

  getResult() {
    return this.result;
  }

  reset() {
    this.result = 0;
    return this;
  }
}
+++++++ REPLACE"
]
END_ARG
```

Same happened with Qwen 2.5-Coder 32B, here was the output:

assistant
To remove the comments from `test.js`, I will use the `search_and_replace_in_file` tool to target and remove the comment lines. Here is the
assistant
 tool call:

```tool
TOOL_NAME: search_and_replace_in_file
BEGIN_ARG: filepath
test.js
END_ARG
BEGIN_ARG: diff
assistant
[
"------- SEARCH
// TODO: Implement subtraction logic
=======
+++++++ REPLACE",
"------- SEARCH
// Prevent division by zero
=======
+++++++ REPLACE"
assistant
]
END_ARG
```

This will remove the specific comment lines found in the `grep_search` output. If there are more comments to remove, I will
assistant
 need to identify them and add more SEARCH/REPLACE blocks accordingly.

It really feels like it's working, maybe just a small parsing issue? Other than this and making the thing experimental I am 100% behind this PR