add dockerfile for unstable, use forky-slim in the forky dockerfile

Author: jakoch

.devcontainer/debian/README.MD

@@ -0,0 +1,12 @@
+# Debian Version Overview
+
+<https://www.debian.org/releases/>
+
+Debian always has three releases in active maintenance: stable, testing and unstable.
+
+| Version | Code Name | Release Date | End of Life (EOL) | End of LTS | End of ELTS | Suite      | Status                         |
+|:-------:|:---------:|:------------:|:-----------------:|:----------:|:-----------:|:-----------|:-------------------------------|
+| 15      | Duke      | TBA          | TBA               | TBA        | TBA         | **unstable**   | Active Development Branch  |
+| 14      | Forky     | TBA          | TBA               | TBA        | TBA         | **testing**    | "packages in the acceptance queue for stable" |
+| 13      | Trixie    | 2025-08-09   | 2028-08-09        | 2030-06-30 | 2035-06-30  | **stable**     | Current stable release         |
+| 12      | Bookworm  | 2023-06-10   | 2026-06-10        | 2028-06-30 | 2033-06-30  | oldstable  | Current oldstable release      |

.devcontainer/debian/bookworm/Dockerfile

@@ -16,7 +16,7 @@
 #
 
 # /===========================================================================\
-# | Debian Bookworm                                                           |
+# | Debian 12 - Bookworm                                                      |
 # |===========================================================================|
 # |                                                                           |
 # | Package Versions                                            (os upstream) |

.devcontainer/debian/forky/Dockerfile

@@ -16,7 +16,7 @@
 #
 
 # /===========================================================================\
-# | Debian 14 - Forky                                                         |
+# | Debian 14 - Forky - Testing                                               |
 # |===========================================================================|
 # |                                                                           |
 # | Package Versions                                            (os upstream) |
@@ -65,8 +65,7 @@ ARG MESA_VERSION=25.0.7
 # - /tmp/vulkansdk.xz
 # - /tmp/mesa.xz
 
-FROM debian:unstable-slim AS downloader
-#FROM debian:forky-slim AS downloader
+FROM debian:forky-slim AS downloader
 
 # Reuse global arguments
 #ARG GCC_VERSION
@@ -95,8 +94,7 @@ RUN echo "Download Stage" && \
 # | BASE IMAGE                  |        See https://hub.docker.com/_/debian
 # +-----------------------------+
 
-FROM debian:unstable-slim AS cpp-devbox-base
-#FROM debian:forky-slim AS cpp-devbox-base
+FROM debian:forky-slim AS cpp-devbox-base
 
 # +-----------------------------+
 # | REUSE GLOBAL ARGS           |

.devcontainer/debian/trixie/Dockerfile

@@ -16,7 +16,7 @@
 #
 
 # /===========================================================================\
-# | Debian Trixie                                                             |
+# | Debian 13 - Trixie                                                        |
 # |===========================================================================|
 # |                                                                           |
 # | Package Versions                                            (os upstream) |