Fix didChange out-of-range crash in ollama_lsp

[cmtonkinson]

Summary

Fixes a crash in python/ollama_lsp.py when handling textDocument/didChange events with ranges that are missing or out of bounds.

Problem

on_change assumed:

• change.range is always present
• change.range.start.line is always within document.lines
• change.range.start.character is always within the current line

In real edit/delete flows, those assumptions can be violated, causing exceptions and the Neovim client to exit with code 1.

Changes

In python/ollama_lsp.py (on_change):

• return early if change.range is missing/None
• return early if start.line >= len(lines)
• guard start.character before slicing the current line (use empty suffix if out of range)

This keeps behavior unchanged for valid edits while avoiding crashes on edge-case range payloads.

Validation

• python3 -m py_compile python/ollama_lsp.py
• validated in Neovim using local plugin dir
• confirmed ollama_lsp stays attached after edit operations that previously caused exits