Hello,
If Your goal is to send everything into ge-0/0/1 when it is up/up, then You won't be able to do it with generate route. Static 0/0 with next-hop 84.10.109.1 is the solution.
If Your goal is to announce 0/0 route when ge-0/0/1 is up/up, then use "aggregate" route with discard NH, it will consider 84.10.109.0/31 as contributor.
JUNOS CLI:
set policy-options policy-statement generate term 1 from protocol direct set policy-options policy-statement generate term 1 from route-filter 84.10.109.0/31 exact set policy-options policy-statement generate term 1 then accept set policy-options policy-statement generate term 2 then reject set routing-options aggregate route 0.0.0.0/0 policy generate
set routing-options aggregate route 0.0.0.0/0 discard ## not strictly necessary but stops wasteful ICMP Unreach generation
And then match appropriately in Your IGP/BGP export policies.
HTH
Thx
Alex