Release v0.51.304 — Release JT (stage-p2a — un-held terminal reaper + opt-in Docker GPU) (#3757)

* fix(terminal): reap reparented terminal descendants by process group (#3725, #2577)

Embedded-terminal descendants reparented to the WebUI process could linger as
zombies. The reaper now calls os.waitpid(-terminal_pgid, WNOHANG) scoped to the
terminal's own process group (terminals spawn with start_new_session=True, so
proc.pid == pgid) rather than process-wide waitpid(-1), which would otherwise
reap unrelated WebUI subprocess children and silently coerce their exit codes to
0. Bounded by a 64-iteration limit and lock-guarded. Runs on reader cleanup and
terminal close.

Co-authored-by: rodboev <rodboev@users.noreply.github.com>

* docs(docker): add opt-in GPU runtime image path (#3721, #3243)

The default image stays CPU-only. A new INSTALL_GPU_LIBS=1 build arg installs
VA-API user-space libraries for users passing through host GPU devices, and
docker_init.bash preserves Docker --group-add supplemental groups (e.g. render/
video for /dev/dri) when dropping privileges to the runtime user. Default
(INSTALL_GPU_LIBS=0) is a no-op. Docs + regression test included.

Co-authored-by: rodboev <rodboev@users.noreply.github.com>

* docs(changelog): stamp v0.51.304 — Release JT (stage-p2a #3725 #3721)

---------

Co-authored-by: nesquena-hermes <[email protected]>
Co-authored-by: rodboev <rodboev@users.noreply.github.com>

Dockerfile

@@ -30,6 +30,26 @@ RUN apt-get update -y --fix-missing --no-install-recommends \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/*
 
+# Optional GPU user-space acceleration libraries for users who pass through
+# host GPU devices. The default image remains CPU-only.
+ARG INSTALL_GPU_LIBS=0
+RUN if [ "$INSTALL_GPU_LIBS" = "1" ]; then \
+        apt-get update -y --fix-missing --no-install-recommends \
+        && apt-get install -y --no-install-recommends \
+            libva2 \
+            vainfo \
+            mesa-va-drivers \
+        && if apt-cache show intel-media-va-driver-non-free >/dev/null 2>&1; then \
+            apt-get install -y --no-install-recommends intel-media-va-driver-non-free; \
+        else \
+            echo "intel-media-va-driver-non-free is not available from the configured Debian repositories; skipping Intel non-free VA-API driver."; \
+        fi \
+        && apt-get clean \
+        && rm -rf /var/lib/apt/lists/*; \
+    else \
+        echo "Skipping optional GPU user-space acceleration libraries (INSTALL_GPU_LIBS=0)."; \
+    fi
+
 # UTF-8
 RUN localedef -i en_US -c -f UTF-8 -A /usr/share/locale/locale.alias en_US.UTF-8
 ENV LANG=en_US.utf8