tools/mcp: pin mcp<2 to fix unit CI collection (#2026)

### What does this PR do?

**Type of change:** Bug fix (CI)

`mcp==2.0.0` was released and removed the `mcp.server.fastmcp` module
(the 2.0 SDK replaces it with `mcp.server.mcpserver`).
`tools/mcp/pyproject.toml` declared an unpinned `mcp>=1.0`, so CI now
resolves `mcp==2.0.0`, and `tools/mcp/modelopt_mcp/server.py`'s `from
mcp.server.fastmcp import FastMCP` fails at import:

```
ModuleNotFoundError: No module named 'mcp.server.fastmcp'
ERROR collecting tools/mcp/tests/test_bridge.py
```

This breaks the `mcp` unit job — and thus the `unit-pr-required-check`
gate — on **every** PR whose diff touches `pyproject.toml`,
`noxfile.py`, or `.github/workflows/unit_tests.yml` (the changed-files
paths that trigger the `mcp` job).

This PR pins `mcp>=1.0,<2`, keeping the 1.x line that still ships
`mcp.server.fastmcp`. Migrating the server to the mcp 2.0 API
(`mcp.server.mcpserver`) is a larger change tracked separately.

### Usage

```python
# N/A - dependency pin only
```

### Testing

- `uv pip install -e tools/mcp` now resolves an `mcp` 1.x wheel, so
`from mcp.server.fastmcp import FastMCP` imports and
`tools/mcp/tests/test_bridge.py` collects again.

### Before your PR is "*Ready for review*"

- Is this change backward compatible?: ✅
- If you copied code from any other sources or added a new PIP
dependency, did you follow guidance in `CONTRIBUTING.md`: N/A — tightens
an existing dependency's upper bound.
- Did you write any new necessary tests?: N/A — restores collection of
the existing `tools/mcp` tests.
- Did you update Changelog?: N/A — CI/build fix, nothing user-facing in
the wheel.
- Did you get Claude approval on this PR?: ❌

### Additional Information

Unblocks the `unit-pr-required-check` gate for in-flight PRs (surfaced
on #2000). Follow-up: migrate `modelopt_mcp/server.py` to the mcp 2.0
API and relax the pin.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Bug Fixes**
* Prevented compatibility issues by limiting the MCP package to
supported version 1.x releases.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Signed-off-by: Fridah-nv <201670829+Fridah-nv@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

tools/mcp/pyproject.toml

@@ -4,7 +4,7 @@ version = "0.1.0"
 description = "MCP server exposing ModelOpt launcher operations (submit, status, logs) as typed tools for codex / Claude Code agents"
 requires-python = ">=3.10"
 dependencies = [
-    "mcp>=1.0",
+    "mcp>=1.0,<2",  # server.py imports mcp.server.fastmcp, removed in mcp 2.0
     "modelopt-launcher",
     "pyyaml",
     "pydantic>=2.0",