assistant: Partial fix for HTML entities in tools params (#32148)

This problem seems to be specific to Opus 4. Eval shows improvement from
89% to 97%.

Closes: https://github.com/zed-industries/zed/issues/32060

Release Notes:

- N/A

Co-authored-by: Ben Brandt <benjamin.j.brandt@gmail.com>

assets/prompts/assistant_system_prompt.hbs

@@ -17,13 +17,13 @@ You are a highly skilled software engineer with extensive knowledge in many prog
 4. Use only the tools that are currently available.
 5. DO NOT use a tool that is not available just because it appears in the conversation. This means the user turned it off.
 6. NEVER run commands that don't terminate on their own such as web servers (like `npm run start`, `npm run dev`, `python -m http.server`, etc) or file watchers.
+7. Avoid HTML entity escaping - use plain characters instead.
 
 ## Searching and Reading
 
 If you are unsure how to fulfill the user's request, gather more information with tool calls and/or clarifying questions.
 
 {{! TODO: If there are files, we should mention it but otherwise omit that fact }}
-{{#if has_tools}}
 If appropriate, use tool calls to explore the current project, which contains the following root directories:
 
 {{#each worktrees}}
@@ -38,7 +38,6 @@ If appropriate, use tool calls to explore the current project, which contains th
 - As you learn about the structure of the project, use that information to scope `grep` searches to targeted subtrees of the project.
 - The user might specify a partial file path. If you don't know the full path, use `find_path` (not `grep`) before you read the file.
 {{/if}}
-{{/if}}
 {{else}}
 You are being tasked with providing a response, but you have no ability to use tools or to read or write any aspect of the user's system (other than any context the user might have provided to you).