Slow imports

# timing

Is it really ok that it takes 209ms to import even a single type from this package?

This feels like the _perfect_ task for Claude Code?!

I have no background in the best way to solve this issue, I just know this feels wrong for such a central dependency. And common, let's be honest, this is a glorified HTTP client.

This destroys downstream performance in packages like `langchain_anthropic` which wind up taking 300ms+ for imports alone, just to make a simple http call to generate a completion!

```sh
python3 -X importtime -c "import anthropic"

...
import time: 66 | 69232 | anthropic.lib.tools
...
import time: 506 | 116232 | anthropic.types
...
import time: 329 | 209401 | anthropic
```

```sh
python3 -X importtime -c "from anthropic.types.image_block_param import ImageBlockParam"
...
import time: 313 | 208162 | anthropic
import time: 7 | 208169 | anthropic.types
import time: 10 | 208178 | anthropic.types.image_block_param
```

I'd hate to think that just because it's python it's ok to ignore optimizations... but, perhaps my expectations are miscalibrated, I'm open to that possibility. Am I crazy?

# Claude seems to agree

I've got Claude working on some ideas for me! I don't have time to do this myself, but, Claude is killing it with perf profiling and I bet will find the spots we can get some big wins.

Gotta tame the explosion of types and importing all of them on every import basically