Updater messages without "!", README and changelog for v0.9

cmd drops "!" from messages when delayed expansion is on, so errors
read "ERROR:". README describes the two files per system and the
first install from a release zip.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/CHANGES-v0.9.md

@@ -0,0 +1,9 @@
+# Technician tool v0.9 - changes
+
+- Two files per system for technicians: `update_windows.bat` / `update_macos.command` (update) and
+  `run_windows.bat` / `run_macos.command` (start).
+- Update: checks Gitea for the newest release tag `vX.Y`, downloads only what changed (git), shows the list of
+  changes, protects files edited by hand (asks first), connects a folder unpacked from a release zip on first
+  run, installs git / uv when missing (asks first) and brings the Python libraries up to date.
+- One shared Python environment for all versions: `KotaTechnicianTool/venv` (was `venv-0.x` per version).
+- A developer copy on a branch is left alone by the update script (use `git pull`).