Windows: product names, the editors, WSL; the Linux page's image step

Assembled from development commit c3c40f6c8fca. Since 830b193: on Windows the
products carry Windows names (ktext.exe, klammertext.dll, document.dll,
reflect.dll) and the console's output code page is UTF-8 for a run; the
editor tooling works on Windows (VS Code, Sublime Text, Vim, with the
interpreter's name chosen by platform) and Notepad++ joins it
(doc/edit/notepadpp: a User Defined Language and two Run-menu commands);
a sixth install page, doc/install/windows_wsl_install.md, for Linux
inside WSL; the Windows page opens with the three routes and gains its
editor section, the PowerShell quoting and Path notes; the Linux page
installs OpenImageIO from the python3-openimageio package and verifies
with kdiag --machine; the README lists all six install pages. Linux and
macOS behaviour is unchanged.

env/makefile.env

@@ -63,14 +63,16 @@ SHARED          = -dynamiclib
 SONAME          = -install_name @rpath/$(notdir $@)
 ORIGIN         := @loader_path
 EXPORT_DYNAMIC  = -Wl,-export_dynamic
+EXE            :=
+DSO            := .so
+KLAMMERTEXT_LIBFILE := libklammertext.so
 else ifneq (,$(filter MINGW% MSYS%,$(UNAME_S)))
 # ---------- Windows (MSYS2, UCRT64 environment; native PE binaries) ----------
 # uname says MINGW64_NT-... under UCRT64 too. The compilers come from the
 # environment's PATH (/ucrt64/bin). libdl.a is the mingw-w64-dlfcn shim over
 # LoadLibrary, linked statically so no libdl.dll travels with the products.
 # PE has no soname and no rpath; a DLL is found through PATH or
-# the executable's own directory, and GNU ld's -l search list on PE does not
-# include ".so", hence the exact-name form below.
+# the executable's own directory.
 GCC            := g++
 CLANG          := clang++
 LDFLAGS         =
@@ -79,15 +81,20 @@ SHARED          = -shared
 SONAME          =
 ORIGIN         := $$ORIGIN
 EXPORT_DYNAMIC  = -Wl,--export-all-symbols
-KLAMMERTEXT_LIB = -l:libklammertext.so
+EXE            := .exe
+DSO            := .dll
+KLAMMERTEXT_LIBFILE := klammertext.dll
 # A Windows program finds a DLL through PATH or its own directory, never an
 # rpath. So every directory that holds a program or a Python extension also
-# holds the DLLs it needs: libklammertext.so and the three gcc runtime DLLs
+# holds the DLLs it needs: klammertext.dll and the three gcc runtime DLLs
 # the toolchain links (from the compiler's own bin/). com/ and kpy/ copy them.
 GCC_BIN         := $(dir $(shell cygpath -m "$$(command -v g++)"))
 GCC_RUNTIME_DLLS := libstdc++-6.dll libgcc_s_seh-1.dll libwinpthread-1.dll
 else
 # ---------- Linux ----------
+EXE            :=
+DSO            := .so
+KLAMMERTEXT_LIBFILE := libklammertext.so
 GCC            := /usr/bin/g++
 CLANG          := $(shell command -v clang++-18 2>/dev/null || command -v clang++ 2>/dev/null)
 LDFLAGS         = -L/usr/lib/x86_64-linux-gnu
@@ -97,8 +104,21 @@ SONAME          = -Wl,-soname,$(notdir $@)
 ORIGIN         := $$ORIGIN
 EXPORT_DYNAMIC  = -rdynamic
 endif
-# How a link line names libklammertext (set above for Windows).
-KLAMMERTEXT_LIB ?= -lklammertext
+# Product names (decided 2026-09-25: Windows users get Windows names).  The
+# three variables above are set per platform: EXE is the executable suffix
+# (".exe" on Windows, none elsewhere), DSO the suffix of a shared object
+# loaded at run time (".dll" / ".so": document$(DSO), reflect$(DSO)), and
+# KLAMMERTEXT_LIBFILE the library's file name (klammertext.dll /
+# libklammertext.so).  A make target carries the suffix so that the file the
+# compiler writes IS the target: bin/ktext never existed on Windows -- gcc
+# wrote ktext.exe -- and every make relinked the three commands.  The engine's
+# own copy of the DSO suffix is shared_library_suffix in mac/file.h.
+#
+# One link form everywhere: GNU ld's -l search list on PE ends with
+# "<name>.dll", so -lklammertext finds klammertext.dll as it finds
+# libklammertext.so on Linux (it did NOT find a DLL called libklammertext.so,
+# which needed the exact-name -l: form).
+KLAMMERTEXT_LIB = -lklammertext
 
 # Resolve the compiler choice (gcc by default; clang with COMPILER=clang).
 CXX := $(if $(filter clang,$(COMPILER)),$(CLANG),$(GCC))