Add editor tooling configuration

clangd fallback flags, clang-format style, clang-tidy checks, and gitignore for the autotools-generated artifacts.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <[email protected]>

.clang-format

@@ -0,0 +1,15 @@
+# .clang-format — nulsl-libc style.
+#
+# Rule of thumb: 4-space indent, 100 columns, allman braces off, keep it
+# boring. Run `clang-format -i` on your diff before opening a PR.
+
+BasedOnStyle: LLVM
+IndentWidth: 4
+ColumnLimit: 100
+PointerAlignment: Left
+DerivePointerAlignment: false
+SortIncludes: true
+BreakBeforeBraces: Attach
+AllowShortFunctionsOnASingleLine: Empty
+AllowShortIfStatementsOnASingleLine: Never
+AllowShortLoopsOnASingleLine: false

.clang-tidy

@@ -0,0 +1,19 @@
+# .clang-tidy — nulsl-libc lint configuration.
+#
+# The linter's job is to yell about bugs, not style (style belongs to
+# clang-format). Keep the check list tight and useful.
+
+# A libc owns the reserved namespace by definition (_exit, environ, ...);
+# bugprone-reserved-identifier only makes sense for application code.
+Checks: >
+  clang-analyzer-*,
+  bugprone-*,
+  performance-*,
+  portability-*,
+  -bugprone-easily-swappable-parameters,
+  -bugprone-implicit-widening-of-multiplication-result,
+  -bugprone-reserved-identifier
+
+WarningsAsErrors: ''
+HeaderFilterRegex: 'include/.*'
+FormatStyle: file

.clangd

@@ -0,0 +1,19 @@
+# .clangd — LSP configuration for nulsl-libc.
+#
+# Fallback flags used when compile_commands.json is absent. After running
+# `make compile_commands` (requires bear), clangd uses the exact build
+# flags from bin/release/ instead, and these are merged on top.
+CompileFlags:
+  Compiler: clang
+  Add:
+    - -std=c17
+    - -Iinclude
+    - -ffreestanding
+    - -fno-builtin
+    - -Wall
+    - -Wextra
+
+# Treat all headers as project headers so warnings apply inside them.
+Diagnostics:
+  Suppress:
+    - unknown-pragmas

.gitignore

@@ -1,49 +1,50 @@
-# ---> C
-# Prerequisites
-*.d
+# Generated by autotools
+aclocal.m4
+autom4te.cache/
+build-aux/
+config.guess
+config.h.in
+config.log
+config.status
+config.sub
+configure
+configure.lineno
+depcomp
+install-sh
+ltmain.sh
+missing
+Makefile.in
 
-# Object files
+# Build artifacts
 *.o
+*.a
+*.lo
+*.la
+.deps/
+.libs/
+
+# Generic C artifacts (for experiments outside the autotools flow)
 *.ko
 *.obj
 *.elf
-
-# Linker output
 *.ilk
 *.map
 *.exp
-
-# Precompiled Headers
 *.gch
 *.pch
-
-# Libraries
 *.lib
-*.a
-*.la
-*.lo
-
-# Shared objects (inc. Windows DLLs)
 *.dll
 *.so
 *.so.*
 *.dylib
-
-# Executables
 *.exe
 *.out
 *.app
-*.i*86
-*.x86_64
 *.hex
-
-# Debug files
 *.dSYM/
 *.su
 *.idb
 *.pdb
-
-# Kernel Module Compile Results
 *.mod*
 *.cmd
 .tmp_versions/
@@ -52,3 +53,16 @@ Module.symvers
 Mkfile.old
 dkms.conf
 
+# Out-of-tree build dirs (the driver Makefile owns these)
+bin/release/*
+!bin/release/.gitkeep
+bin/debug/*
+!bin/debug/.gitkeep
+
+# LSP (generated by `make compile_commands`)
+compile_commands.json
+
+# Editor/agent caches
+.cache/
+.omo/
+*~