feat(rules): a rule can carry its own check — verify_with, expires_when, verified_at (#3095, milestone 312 step 1)

A rulebook holds two kinds of row in one table. A NORM is a decision: no
truth value, changes only when its author changes it, and they know they
did. A CONSTRAINT asserts a fact about someone else's software, and goes
false with nobody present. Milestone 307's audit found nine stale sites;
every one was a constraint, and not one norm had rotted.

Three nullable columns so a rule can say how to check itself. expires_when
is a STATE, not a date — constraints expire when the ground moves, not on a
schedule. verified_at NULL means never checked and sorts FIRST in the sweep
to come: unexamined outranks examined-long-ago. Most rules set none of the
three; a null verify_with is the marker for "this is a decision, there is
nothing to go and check," and it only reads that way while it stays honest.

Nothing is backfilled and nothing is indexed. A migration cannot invent a
check any more than 0088 could invent a trigger, and the sweep reads a whole
rulebook — hundreds of rows, on operator demand, never on a request path.

Also, in the backup service the fields had to pass through:

- Restore now remaps arose_from_id through note_id_map. It has been exported
  since 0088 and silently dropped on the way back in ever since, so every
  restore lost every rule's provenance link.
- _dt_or_none, because _dt substitutes now() for an absent value. That is
  right for created_at/updated_at and wrong here: a rule nobody ever checked
  would restore looking freshly checked and fall to the bottom of the sweep
  it should top.

Column additions do not move BACKUP_VERSION; only new sections do, as when
0088 added when_to_apply/tier/arose_from_id to the same helper.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/scribe/models/rulebook.py

@@ -107,6 +107,26 @@ class Rule(Base, TimestampMixin, SoftDeleteMixin):
     tier: Mapped[str] = mapped_column(Text, default="always_on", server_default="always_on")
     why: Mapped[str | None] = mapped_column(Text, nullable=True)
     how_to_apply: Mapped[str | None] = mapped_column(Text, nullable=True)
+    # The three fields that tell a CONSTRAINT apart from a NORM (milestone
+    # 312). A norm is a decision — no truth value, changes only when its
+    # author changes it. A constraint asserts a fact about someone else's
+    # software, and goes false with nobody watching: every stale rule the
+    # 307 audit found was one, and no norm had rotted.
+    #
+    # `verify_with` is how to check the rule is still true; `expires_when` is
+    # the STATE that ends it, deliberately not a date — constraints expire
+    # when the ground moves, not on a schedule. `verified_at` NULL means
+    # never checked, and sorts FIRST in the sweep: unexamined outranks
+    # examined-long-ago.
+    #
+    # Most rules should leave all three empty. A null `verify_with` is not a
+    # gap — it is the marker for "this is a decision, there is nothing to go
+    # and check," and the signal is only worth reading while that stays true.
+    verify_with: Mapped[str | None] = mapped_column(Text, nullable=True)
+    expires_when: Mapped[str | None] = mapped_column(Text, nullable=True)
+    verified_at: Mapped[datetime | None] = mapped_column(
+        DateTime(timezone=True), nullable=True
+    )
     # The record that caused this rule — the edge notes and tasks already
     # have. Rule 46's `why` names note 2813 in prose; this is that link as a
     # field, so it survives a rewording of the paragraph.
@@ -126,6 +146,9 @@ class Rule(Base, TimestampMixin, SoftDeleteMixin):
             "tier": self.tier,
             "why": self.why or "",
             "how_to_apply": self.how_to_apply or "",
+            "verify_with": self.verify_with or "",
+            "expires_when": self.expires_when or "",
+            "verified_at": iso(self.verified_at),
             "arose_from_id": self.arose_from_id,
             "order_index": self.order_index,
             "created_at": iso(self.created_at),