Add Go statusline implementation

Replace shell-based statusline with native Go for ~4x speedup.
Parses JSON natively, detects git status, checks gitea process,
and formats colored output with proper terminal width handling.

.gitignore

@@ -0,0 +1,45 @@
+/statusline
+/bin
+
+# Created by https://gitignore.kjanat.com/api/go,linux
+# Edit at https://gitignore.kjanat.com?templates=go,linux
+
+### Go ###
+# If you prefer the allow list template instead of the deny list, see community template:
+# https://github.com/github/gitignore/blob/main/community/Golang/Go.AllowList.gitignore
+#
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+
+# Test binary, built with `go test -c`
+*.test
+
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out
+
+# Dependency directories (remove the comment below to include it)
+# vendor/
+
+# Go workspace file
+go.work
+
+### Linux ###
+*~
+
+# temporary files which can be created if a process still has a handle open of a deleted file
+.fuse_hidden*
+
+# KDE directory preferences
+.directory
+
+# Linux trash folder which might appear on any partition or disk
+.Trash-*
+
+# .nfs files are created when an open file is removed but is still being accessed
+.nfs*
+
+# End of https://gitignore.kjanat.com/api/go,linux