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.

doc/install/linux_source_install.md

@@ -7,6 +7,8 @@ including `:haskell` and `:shell` commands that depend on locally installed
 software.
 
 For the container installation on Linux, see `linux_container_install.md`.
+On Windows, this page also applies unchanged inside the Windows Subsystem
+for Linux; `windows_wsl_install.md` says what is specific to WSL.
 
 
 ## Prerequisites
@@ -21,15 +23,19 @@ sudo apt-get install g++ make python3-dev
 The C++ compiler must support C++20. GCC 11 or later is required (Ubuntu 22.04
 and later include GCC 12+).
 
-The SKS `@image` klammer requires OpenImageIO Python bindings. These must match
-the Python version that ktext is built against (check with
-`python3.XX -c "import OpenImageIO"`). For example, if ktext links against
-Python 3.12:
+The SKS `@image` klammer requires the OpenImageIO Python bindings, for the
+same Python that ktext is built against (the system `python3`). Ubuntu
+packages them:
 
 ```bash
-pip3.12 install OpenImageIO
+sudo apt-get install python3-openimageio
+python3 -c "import OpenImageIO"
 ```
 
+(A `pip` install works too, but a fresh Ubuntu has no `pip` until
+`python3-pip` is installed, and since 24.04 it refuses to install into the
+system Python without `--break-system-packages`; the package avoids both.)
+
 Verify:
 
 ```bash
@@ -284,8 +290,8 @@ ktext -s '@eval 1 + 1 @' -d
 # Shell evaluation
 ktext -s '@eval :shell date @' -d
 
-# Show machine state (SKS is loaded by default)
-ktext -s '' -m
+# Show the machine's initial state: targets, argument types, the primitive klammers
+kdiag --machine
 
 # HTML and PDF output (uses the hello.kt from the Build section)
 ktext hello.kt -t html