fix(context): normalize file paths for Windows compatibility (v2)

[john-mutuma]

Summary

• Updated fix for file context path normalization on Windows
• Previous fix only normalized nvim_buf_get_name when ctx.name was nil — now normalizes ALL paths including pre-set ctx.name from pickers and textobject contexts
• Also normalizes vim.fs.relpath output which may return backslash paths on Windows

[john-mutuma]

Superseded by direct commit to main (36c407f).