Mismatch in python version and outdated causing broken installs.

## Problem

Installing dev dependencies fails because package pins conflict:

* `gevent==23.9.1` requires `greenlet>=2.0.0`
* The project pins `greenlet==1.1.2`

So this command cannot resolve dependencies:

```bash id="t0j8k2"
uv pip install -r requirements-dev.txt
```
Additionally the `runtime` version is not also right.

## Solution

Upgrade `greenlet` to **2.0.0 or higher**.

Update `requirements-dev.txt`:

```txt id="w2m9qa"
greenlet>=2.0.0
```

or pin exactly:

```txt id="i7c4nx"
greenlet==2.0.0
```

Then reinstall:

```bash id="f3p1de"
uv pip install -r requirements-dev.txt
```

## Root Cause

`greenlet==1.1.2` is outdated and incompatible with `gevent==23.9.1`.