Bug: Tool examples broken after PR #380 - need MelleaTool wrapper

## Bug: Tool examples broken after PR #380 - need MelleaTool wrapper

### Description
PR #380 introduced a breaking change requiring `MelleaTool` instances instead of raw callables for `ModelOption.TOOLS`. Several examples and documentation were not updated and now fail.

### Failing Tests
- `docs/examples/tools/interpreter_example.py` ✗ (test fails)

### Affected Documentation (not tested but incorrect)
- `docs/examples/tools/README.md` (lines 45, 56, 83, 103)
- `docs/tutorial.md` (line 1359)

### Error
```
AssertionError: If ModelOption.TOOLS is a list, it must be a list of Tool; found <class 'function'>
```

### Root Cause
The tool system now requires wrapping callables with `MelleaTool.from_callable()`:

**Before (broken):**
```python
from mellea.stdlib.tools import local_code_interpreter

m.instruct(
    description="...",
    model_options={ModelOption.TOOLS: [local_code_interpreter]},
)
```

**After (fixed):**
```python
from mellea.stdlib.tools import local_code_interpreter
from mellea.backends.tools import MelleaTool

m.instruct(
    description="...",
    model_options={ModelOption.TOOLS: [MelleaTool.from_callable(local_code_interpreter)]},
)
```

### Files to Update

**Examples (tested):**
- `docs/examples/tools/interpreter_example.py` (lines 21, 33, 63)

**Documentation (not tested but needs update):**
- `docs/examples/tools/README.md` (lines 45, 56, 83, 103)
- `docs/tutorial.md` (line 1359 - `web_search` function)

**Note:** All tests in `test/backends/` already use `MelleaTool.from_callable()` correctly.

### Additional Context
- PR #380: feat: new MelleaTool class and adoption across mellea
- Commit: ffb8b6c797b20ec387a2c2257e88900b4e498f0f
- See `test/backends/test_mellea_tool.py` for correct usage examples

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Bug: Tool examples broken after PR #380 - need MelleaTool wrapper #383