fix(installer): force native rebuild on every run + post-install smoke test

When `npm install --omit=dev` finds the lockfile already satisfied (the
case on upgrade re-runs) it skips touching node_modules — including
prebuilt native binaries. If the host's Node version has drifted since
the original install, the cached better_sqlite3.node has the wrong ABI
and the service crashloops with ERR_DLOPEN_FAILED on first openDb().

We hit this in the wild upgrading a v0.5.0 box (Node 23 at install time)
to v0.6.0 (Node 20 now). The release tarball doesn't ship node_modules
— the bad binary was preserved from the original install.

Now: unconditionally `npm rebuild better-sqlite3` after the install step
so the ABI matches the actual Node binary the service will use, and
fail fast at install time with `node -e "require('better-sqlite3')"`
instead of letting systemd find out the hard way.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: gididaf

install.sh

@@ -275,6 +275,24 @@ fi
 say "Installing production dependencies (this may take a minute)"
 (cd "$INSTALL_DIR" && npm install --omit=dev --no-audit --no-fund --silent) \
   || die "npm install failed. If better-sqlite3 fails to build, install build tools: $PM install -y build-essential python3"
+
+# Force-rebuild native deps against the current Node ABI. Necessary because
+# `npm install` is a no-op when the lockfile is already satisfied (e.g. on
+# upgrade re-runs) and so it doesn't rematerialize prebuilt binaries even
+# when Node has changed under it. Without this, a host whose Node version
+# shifted between installs (Node 23 → Node 20 was the v0.6.0 regression)
+# ends up with a NODE_MODULE_VERSION mismatch and the service crashloops on
+# `openDb()` with ERR_DLOPEN_FAILED.
+say "Rebuilding native modules for $(node --version)"
+(cd "$INSTALL_DIR" && npm rebuild better-sqlite3 --no-audit --no-fund --silent) \
+  || die "npm rebuild better-sqlite3 failed. Install build tools: $PM install -y build-essential python3"
+
+# Fail fast at install time instead of letting systemd discover the ABI
+# mismatch via crashloop. Loads the native module under the same node
+# binary the service will use.
+if ! node -e "require('better-sqlite3')" 2>/dev/null; then
+  die "better-sqlite3 still won't load under $(node --version). Try: cd $INSTALL_DIR && rm -rf node_modules && npm install --omit=dev"
+fi
 ok "Dependencies installed"
 
 # --- Resolve runtime paths for the templated unit ---

package.json

@@ -1,6 +1,6 @@
 {
   "name": "spannora-monorepo",
-  "version": "0.6.0",
+  "version": "0.6.1",
   "private": true,
   "description": "Self-hosted web chat for Claude Code (Agent SDK). Server + hub PWA + shared frontend modules.",
   "workspaces": [