rd: derive schema tree parse on startup rather than recomputing every time

src/eval/eval_ir.c

@@ -74,6 +74,7 @@ e_select_ir_ctx(E_IRCtx *ctx)
     e_ir_state->arena = arena;
     e_ir_state->arena_eval_start_pos = arena_pos(arena);
   }
+  arena_pop_to(e_ir_state->arena, e_ir_state->arena_eval_start_pos);
   e_ir_state->ctx = ctx;
   e_ir_state->used_tag_map       = push_array(e_ir_state->arena, E_UsedTagMap, 1);
   e_ir_state->used_tag_map->slots_count = 64;

src/eval/eval_parse.c

@@ -632,6 +632,7 @@ e_select_parse_ctx(E_ParseCtx *ctx)
     e_parse_state->arena = arena;
     e_parse_state->arena_eval_start_pos = arena_pos(arena);
   }
+  arena_pop_to(e_parse_state->arena, e_parse_state->arena_eval_start_pos);
   e_parse_state->ctx = ctx;
   e_parse_state->parse_cache_slots_count = 1024;
   e_parse_state->parse_cache_slots = push_array(e_parse_state->arena, E_ParseCacheSlot, e_parse_state->parse_cache_slots_count);

src/eval/eval_parse.h

@@ -180,7 +180,7 @@ struct E_ParseCtx
 };
 
 ////////////////////////////////
-//~ rjf: Parse State (Stateful thread-local caching mechanisms, not provided by user)
+//~ rjf: Parse State (stateful thread-local caching mechanisms, not provided by user)
 
 typedef struct E_ParseCacheNode E_ParseCacheNode;
 struct E_ParseCacheNode