Adds a SQL bundle plus event triggers that enforce `INHERITS (hectic.created_at)`
on every user CREATE TABLE and auto-attach a BEFORE UPDATE row trigger when a
table inherits `hectic.updated_at`. Always-exempt: `hectic`, `information_schema`,
`pg_*`, declarative partitions, temp tables. Per-DB opt-out via the GUC
`hectic.inheritance_extra_excluded_schemas`.
Exposed three ways:
* `pkgs.hectic.hectic-inheritance` — derivation with the SQL at
$out/share/hectic/hectic-inheritance.sql
* `self.lib.hecticInheritance.{sql,path}` — pkgs-free Nix surface
* `postgres-init` opt-in via `PG_HECTIC_INHERITANCE=1` (HECTIC_INHERITANCE_SQL
overrides the default)
Test postgres-init-hectic-inheritance covers all six branches: bootstrap,
non-inheriting reject, accepting inheritance, auto updated_at trigger fires,
GUC exclusion, declarative partition exemption.
