GenServer that owns the ETS tables for a single proof session.

Creates the shared, public tables listed below on startup and keeps them alive for the duration of the session tree; they are dropped with this process when the session is torn down. All other processes obtain the table references via get_tables/1.

Tables created:

• :stats — proof-search counters and timing metadata.
• :tombs — branch IDs that have been closed; used to poison descendants.
• :work_queue — ordered set of {priority_key, Branch.t()} entries.
• :idle_queue — branches parked waiting for iterative deepening.
• :traces — per-branch rule application history for proof reconstruction.
• :provenance — per-fresh-variable annotation (γ / prim-subst origin); see ShotTx.Prover.Provenance.
• :idle_workers — {worker_pid, true} for each worker currently parked on an empty queue. Read by ShotTx.Prover.Worker when it pushes a branch, so that a push only wakes workers actually waiting for one.
• :suggestions — instantiation hints published by SuggestionAgent, consumed by workers on splice; see ShotTx.Prover.Suggestion. Rows are {{prefix, recipe, term}, applied_count, %Suggestion{}} so that :ets.update_counter/3 can enforce the cascade cap at position 2.