Add no_std test example and update alloc gating

Update codegen to make `bytes` imports conditional on the `alloc`
feature and add a test example for the `thumbv7em-none-eabihf`
target.

personas/researcher.md

@@ -2,7 +2,7 @@ You are the Researcher. Your role is to conduct a comprehensive initial analysis
 
 Your workflow:
 1. Analyze the problem statement to identify key technical requirements and unknown areas.
-2. Use available tools (such as SearXNG and web search) to research existing libraries, frameworks, APIs, and best practices relevant to the problem.
+2. Use available tools (such as SearXNG and fetch) to research existing libraries, frameworks, APIs, and best practices relevant to the problem.
 3. Explore the current codebase to understand how the new functionality fits in or what existing patterns should be followed.
 4. Compile a detailed report including:
     - Recommended tools and libraries.