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/services/backup.py

@@ -112,6 +112,18 @@ def _dt(val: str | None) -> datetime:
     return datetime.fromisoformat(val) if val else datetime.now(timezone.utc)
 
 
+def _dt_or_none(val: str | None) -> datetime | None:
+    """Like _dt, but keeps an absent timestamp absent.
+
+    _dt substitutes now() because created_at/updated_at must not be null.
+    For a nullable column that MEANS something by being empty, that default
+    is a lie: a rule nobody ever verified would restore looking verified at
+    the moment of the restore, and drop straight to the bottom of the sweep
+    it should have topped.
+    """
+    return datetime.fromisoformat(val) if val else None
+
+
 def _d(val: str | None) -> date | None:
     return date.fromisoformat(val) if val else None
 
@@ -385,6 +397,8 @@ def _rule_rows(rows) -> list[dict]:
             "title": r.title, "statement": r.statement, "why": r.why,
             "how_to_apply": r.how_to_apply, "order_index": r.order_index,
             "when_to_apply": r.when_to_apply, "tier": r.tier,
+            "verify_with": r.verify_with, "expires_when": r.expires_when,
+            "verified_at": r.verified_at.isoformat() if r.verified_at else None,
             "arose_from_id": r.arose_from_id,
             "created_at": r.created_at.isoformat(),
             "updated_at": r.updated_at.isoformat(),
@@ -1007,6 +1021,19 @@ async def _restore_v2(data: dict) -> dict:
                 # is the pre-0088 behaviour, so an old backup restores rules
                 # that bind exactly as they did when it was taken.
                 tier=r_data.get("tier") or "always_on",
+                verify_with=r_data.get("verify_with") or None,
+                expires_when=r_data.get("expires_when") or None,
+                # Restored as-is, NOT reset to null. `verified_at` records
+                # when someone last ran the check; a restore does not make
+                # that untrue, and clearing it would put every constraint at
+                # the top of the sweep with nothing having actually changed.
+                verified_at=_dt_or_none(r_data.get("verified_at")),
+                # Remapped through note_id_map like every other note edge.
+                # Exported since 0088 but dropped on the way back in until
+                # milestone 312 — a restore silently lost every rule's
+                # provenance link. SET NULL semantics apply here too: a
+                # source note that didn't restore leaves the rule intact.
+                arose_from_id=note_id_map.get(r_data.get("arose_from_id") or 0),
                 order_index=r_data.get("order_index", 0),
                 created_at=_dt(r_data.get("created_at")),
                 updated_at=_dt(r_data.get("updated_at")),