feat(ecs): observers and block change stamps on a Table

tb_on_add / tb_on_remove take a fn(int) (its states supplied, like a system's) told each handle as
its row is made and before it goes (ecs_hooks.ludic), so what follows a table - a drawing, a
message - does so without a scan. Every row's tick now also stamps its 64-row block, and
tb_changed_since / tb_added_since skip the blocks nobody wrote since: a delta over a large table
costs the blocks that moved. A row moved into a removal's gap keeps its own tick (it was not
written); a removal is told by the hook. ecs_test holds both. The ludic.wildlife table
(5ac3d48, written while builds were held) now builds and passes its 19 tests.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/ludic.base/index.ludic

@@ -9,6 +9,7 @@ import "save.ludic"
 import "save_fields.ludic"
 import "system.ludic"
 import "ecs_table.ludic"
+import "ecs_hooks.ludic"
 import "ecs_table_remove.ludic"
 import "ecs_table_set.ludic"
 import "ecs_grid.ludic"