fix: docker entrypoint test - set MCP_MODE=http for detached container

Root cause: Test was starting container in detached mode without setting
MCP_MODE. The node application defaulted to stdio mode, which expects
JSON-RPC input on stdin. In detached Docker mode, stdin is /dev/null,
causing the process to receive EOF and exit immediately.

When the test tried to check /proc/1/environ after 3 seconds, PID 1 no
longer existed, causing the helper function to return null instead of
the expected NODE_DB_PATH value.

Solution: Add MCP_MODE=http to the docker run command so the HTTP server
starts and keeps the container running, allowing the test to verify that
NODE_DB_PATH is correctly set in the process environment.

This fixes the last failing CI test in the fix/fts5-search-failures branch.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

tests/integration/docker/docker-entrypoint.test.ts

@@ -240,8 +240,9 @@ describeDocker('Docker Entrypoint Script', () => {
 
       // Use a path that the nodejs user can create
       // We need to check the environment inside the running process, not the initial shell
+      // Set MCP_MODE=http so the server keeps running (stdio mode exits when stdin is closed in detached mode)
       await exec(
-        `docker run -d --name ${containerName} -e NODE_DB_PATH=/tmp/custom/test.db -e AUTH_TOKEN=test ${imageName}`
+        `docker run -d --name ${containerName} -e NODE_DB_PATH=/tmp/custom/test.db -e MCP_MODE=http -e AUTH_TOKEN=test ${imageName}`
       );
       
       // Give it more time to start and stabilize