chore: enforce LF line endings via gitattributes, editorconfig, pre-commit

Introduces a three-layer defence against CRLF/LF drift:

- `.gitattributes` normalizes all text files to LF on commit and checkout;
  Windows-native scripts (*.bat, *.cmd, *.ps1) explicitly keep CRLF.
- `.editorconfig` instructs editors (VS Code, JetBrains, vim, etc.) to save
  with LF by default so the problem is prevented at the source.
- `mixed-line-ending --fix=lf` hook in pre-commit catches anything that
  slips through and auto-fixes it before commit.

No file contents are normalized in this commit — that follows in a
separate `git add --renormalize .` commit for easier review.

.editorconfig

@@ -0,0 +1,21 @@
+root = true
+
+[*]
+end_of_line = lf
+charset = utf-8
+insert_final_newline = true
+trim_trailing_whitespace = true
+indent_style = space
+indent_size = 4
+
+[*.{ts,tsx,js,jsx,mjs,cjs,json,yml,yaml,md,html,css}]
+indent_size = 2
+
+[*.md]
+trim_trailing_whitespace = false
+
+[*.{bat,cmd,ps1}]
+end_of_line = crlf
+
+[Makefile]
+indent_style = tab

.gitattributes

@@ -0,0 +1,51 @@
+# Normalize all text files to LF on commit and checkout.
+# Prevents CRLF drift when contributors work on Windows with core.autocrlf=true.
+* text=auto eol=lf
+
+# Python and shell — LF everywhere, shebangs require it on Unix.
+*.py   text eol=lf
+*.sh   text eol=lf
+
+# Web / config — LF.
+*.ts    text eol=lf
+*.tsx   text eol=lf
+*.js    text eol=lf
+*.jsx   text eol=lf
+*.mjs   text eol=lf
+*.cjs   text eol=lf
+*.json  text eol=lf
+*.yml   text eol=lf
+*.yaml  text eol=lf
+*.toml  text eol=lf
+*.md    text eol=lf
+*.html  text eol=lf
+*.css   text eol=lf
+
+# KiCad project files are text (S-expressions / JSON) — LF.
+*.kicad_sch  text eol=lf
+*.kicad_pcb  text eol=lf
+*.kicad_pro  text eol=lf
+*.kicad_sym  text eol=lf
+*.kicad_mod  text eol=lf
+*.kicad_dru  text eol=lf
+*.kicad_wks  text eol=lf
+*.net        text eol=lf
+
+# Windows-native scripts — must stay CRLF.
+*.bat text eol=crlf
+*.cmd text eol=crlf
+*.ps1 text eol=crlf
+
+# Binary assets — never touch.
+*.png binary
+*.jpg binary
+*.jpeg binary
+*.gif binary
+*.ico binary
+*.pdf binary
+*.zip binary
+*.gz  binary
+*.woff  binary
+*.woff2 binary
+*.ttf   binary
+*.otf   binary

.pre-commit-config.yaml

@@ -4,6 +4,8 @@ repos:
     hooks:
       - id: trailing-whitespace
       - id: end-of-file-fixer
+      - id: mixed-line-ending
+        args: ["--fix=lf"]
       - id: check-yaml
       - id: check-json
       - id: check-added-large-files