fix: enforce LF line endings for shell scripts on all platforms

[Sdaswani]

Summary

• Add .gitattributes to force LF line endings for *.sh and Makefile on checkout across Windows, macOS, and Linux
• Add root .editorconfig so editors consistently use LF for cross-platform files

Problem

On Windows/WSL, shell scripts checked out with CRLF line endings cause bash errors when running dev tooling:

scripts/thunderdoctor.sh: line 2: $'\r': command not found
set: pipefail: invalid option name

This blocks make doctor and other Makefile targets that invoke bash scripts.

Solution

Git already stores these files with LF in the index; the missing piece is checkout normalization via .gitattributes (eol=lf) plus editor guidance via .editorconfig.

Test plan

• Fresh clone into WSL home filesystem (~/thunderbolt-lf-test) — scripts/*.sh and Makefile have LF line endings (no CRLF)
• make doctor runs without CRLF/bash parse errors (fails later only on missing tools, as expected)
• Maintainer verifies on macOS/Linux clone

Notes

Developers with existing Windows checkouts on /mnt/c/ may need a one-time refresh after pulling:

git checkout -- scripts/ Makefile

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Note

Low Risk
Repo-wide editor and Git checkout settings only; no runtime or application logic changes.

Overview
Adds .gitattributes so *.sh and Makefile always check out with LF, fixing CRLF-related bash failures on Windows/WSL when running targets like make doctor. Windows script types (*.bat, *.cmd, *.ps1) stay CRLF; common binary extensions are marked binary.

Adds a root .editorconfig with LF defaults, tab indents for Makefile, CRLF for Windows scripts, and 2-space indent for JSON/YAML/lock files.

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