feat(install): allow overriding the source archive URL (TACHYON_SOURCE_URL)

install.sh

@@ -10,6 +10,9 @@ REPO_HOST="${TACHYON_REPO_HOST:-git.rukavishnikoff.ru}"
 REPO_OWNER="${TACHYON_REPO_OWNER:-hacker07}"
 REPO_NAME="${TACHYON_REPO_NAME:-NeoTachyon}"
 SOURCE_BRANCH="${TACHYON_SOURCE_BRANCH:-main}"
+# Optional explicit archive URL for source installation (mirror, plain HTTP or
+# file://). Defaults to <REPO_INSTALL_URL>/archive/<SOURCE_BRANCH>.tar.gz.
+SOURCE_URL="${TACHYON_SOURCE_URL:-}"
 REPO_INSTALL_URL="${TACHYON_REPO_INSTALL_URL:-https://${REPO_HOST}/${REPO_OWNER}/${REPO_NAME}}"
 
 # ─── TUI helpers (self-contained, no external deps) ─────────────────────────
@@ -3068,7 +3071,11 @@ source_install_from_repo() {
 
     msg "Installing NeoTachyon from source (branch $SOURCE_BRANCH)..."
 
+    if [ -n "$SOURCE_URL" ]; then
+        _archive_url="$SOURCE_URL"
+    else
         _archive_url="${REPO_INSTALL_URL}/archive/${SOURCE_BRANCH}.tar.gz"
+    fi
     _archive_file="${TMP_DIR:-/tmp}/neotachyon-src.tar.gz"
     _src_dir="${TMP_DIR:-/tmp}/neotachyon-src"