🐛 Fix silent download failure and cosmetic naming bugs 🐛

Fixes three bugs discovered during live container testing.
The critical bug was a bash post-increment no-op: `exitCode=$((exitCode++))`
assigns the *old* value back to the variable, so exitCode stays 0 even
when a download fails. This caused the Docker build to succeed silently
when the gitea binary download failed, publishing a broken image to Docker Hub.
- rootfs/root/docker/setup/05-custom.sh: change exitCode=$((exitCode++)) to
exitCode=$((exitCode + 1)) in both the gitea and act_runner failure handlers
- rootfs/usr/local/bin/entrypoint.sh: change CONTAINER_NAME and description
from "archlinux" (copied template default) to "gitea"
- rootfs/usr/local/etc/docker/init.d/08-gitea.sh: remove leading space from
[ -d " /config/ssh" ] path test so the directory existence check is correct

.claude/
rootfs/root/docker/setup/05-custom.sh
rootfs/usr/local/bin/entrypoint.sh
rootfs/usr/local/etc/docker/init.d/08-gitea.sh

rootfs/root/docker/setup/05-custom.sh

@@ -51,7 +51,7 @@ if curl -q -LSsf "$GITEA_URL" -o "/tmp/gitea.$$"; then
 	fi
 else
 	echo "Failed to download gitea" >&2
-	exitCode=$((exitCode++))
+	exitCode=$((exitCode + 1))
 fi
 echo "Downloading act_runner from $ACT_URL"
 if curl -q -LSsf "$ACT_URL" -o "/tmp/act_runner.$$"; then
@@ -60,7 +60,7 @@ if curl -q -LSsf "$ACT_URL" -o "/tmp/act_runner.$$"; then
 	chmod +x "$ACT_BIN_FILE"
 else
 	echo "Failed to download act_runner" >&2
-	exitCode=$((exitCode++))
+	exitCode=$((exitCode + 1))
 fi
 [ -x "$ACT_BIN_FILE" ] && [ -x "$GITEA_BIN_FILE" ] && exitCode=0
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