Bootstrap the per-user Python venv from the wrapper

The Project Manager GUI does not set up O3DE's Python venv itself; it only
errors ("Missing python venv file .../pyvenv.cfg") when it's absent, which
cascades into "Failed to get engine info" / "Failed to initialize". Nothing
was running get_python.sh on launch.

The wrapper now runs python/get_python.sh when python.sh reports the venv is
missing/stale. get_python.sh downloads Python, creates the venv under the
writable ~/.o3de, and installs the o3de CLI from the prebuilt sdist. It is
idempotent and self-heals a half-built venv (venv creation uses --clear).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

o3de-wrapper.sh

@@ -27,4 +27,24 @@ fi
 # Make libraries that sit next to the binary discoverable too.
 export LD_LIBRARY_PATH="$(dirname "$O3DE_BIN"):${LD_LIBRARY_PATH}"
 
+# Bootstrap O3DE's per-user Python venv if needed. The Project Manager GUI does
+# NOT set this up itself - it just errors out ("Missing python venv file ...") if
+# the venv is absent. So we ensure it here. python.sh exits non-zero when the
+# venv for this engine is missing/stale; get_python.sh then downloads Python,
+# creates the venv (~/.o3de/Python, writable) and installs the 'o3de' CLI from
+# the prebuilt sdist. It is idempotent and self-healing (recreates a broken venv
+# with --clear). cmake, needed for the engine-id calc, ships in the Sdk runtime.
+PYTHON_SH=$(find "$O3DE_ROOT" -type f -path '*/python/python.sh' 2>/dev/null | head -n 1)
+GET_PYTHON=$(find "$O3DE_ROOT" -type f -path '*/python/get_python.sh' 2>/dev/null | head -n 1)
+if [ -n "$GET_PYTHON" ]; then
+    if ! "$PYTHON_SH" --version >/dev/null 2>&1; then
+        echo "O3DE: setting up the per-user Python environment." >&2
+        echo "O3DE: first launch downloads Python and can take several minutes..." >&2
+        if ! "$GET_PYTHON"; then
+            echo "error: O3DE Python setup failed (see the log above)." >&2
+            exit 1
+        fi
+    fi
+fi
+
 exec "$O3DE_BIN" "$@"