[FEATURE]: Support LSP detection via shebang line for extensionless scripts

[manicolosi]

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

Scripts without file extensions (e.g., PEP 723 scripts using uv run --script) don't get LSP support because detection is extension-only.

Example:

#!/usr/bin/env -S uv run --script
# /// script
# requires-python = ">=3.11"
# ///

This file has no .py extension but should use pyright.

Proposed solution:

Parse shebang line as fallback when no extension matches. Support common patterns like uv run, python, node, bash, etc.