feat(rulings): a command or edit touching an area's files shows its rulings, once per session (milestone 444 step 4, #4757)

A System's rulings (the Rulings section of its description) now reach the
work by path, not by similarity. Both PreToolUse arms resolve the files a
command or edit names to the Systems whose path_patterns cover them, and the
first touch in a session shows each area's rulings in one line; a repeat is
a one-line reference. A lookup, so no floor, no budget, no retrieval_logs row.

- services/system_rulings: parse_rulings, command_paths (reads and writes,
  relative to the repo root from any cwd; flags, URLs, globs skipped),
  rulings_for_paths
- /tool-rules takes root, cwd and seen_ruling_systems; /prior-art takes
  seen_ruling_systems; both return ruling_system_ids
- hooks share <sid>.rulings.ids (cleared on compaction by the ledger naming
  convention); the Bash hook sends the repo root and cwd
- system_usage_events (migration 0114): surfacings by source, pulls from
  get_system; carried by backup (v20) through the system map
- writing-records: rulings also arrive when the area's files are touched

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

src/scribe/models/__init__.py

@@ -60,6 +60,7 @@ from scribe.models.retrieval_log import RetrievalLog  # noqa: E402, F401
 from scribe.models.retrieval_tuning import RetrievalTuningEvent  # noqa: E402, F401
 from scribe.models.note_usage import NoteUsageEvent  # noqa: E402, F401
 from scribe.models.rule_usage import RuleUsageEvent  # noqa: E402, F401
+from scribe.models.system_usage import SystemUsageEvent  # noqa: E402, F401
 from scribe.models.project import Project  # noqa: E402, F401
 from scribe.models.milestone import Milestone  # noqa: E402, F401
 from scribe.models.task_log import TaskLog  # noqa: E402, F401

src/scribe/models/system_usage.py

@@ -0,0 +1,56 @@
+from sqlalchemy import BigInteger, Index, Text
+from sqlalchemy.orm import Mapped, mapped_column
+
+from scribe.models import Base
+from scribe.models.base import CreatedAtMixin, iso
+
+SURFACED = "surfaced"
+PULLED = "pulled"
+
+
+class SystemUsageEvent(Base, CreatedAtMixin):
+    """One row per time a System's rulings were SHOWN to the agent because its
+    files were touched, or the System was PULLED in full (milestone 444).
+
+    The third of the usage tables, after `note_usage_events` and
+    `rule_usage_events`, and separate from both for the reason the rule twin
+    gives: identity at restore. A System id is its own namespace, mapped
+    through the restore's system map; parked in either sibling's id column it
+    would come back attached to whatever note or rule took that number.
+
+    What it answers: whether an area's rulings, delivered by path rather than
+    by a ranker, are then read (`get_system`) — and so whether delivery by
+    path earns its line.
+
+    FK-free on `system_id`, `user_id` and `project_id`, like its siblings:
+    telemetry outlives the row it describes.
+    """
+
+    __tablename__ = "system_usage_events"
+
+    id: Mapped[int] = mapped_column(BigInteger, primary_key=True)
+    user_id: Mapped[int | None] = mapped_column(BigInteger, nullable=True)
+    system_id: Mapped[int] = mapped_column(BigInteger, nullable=False)
+    # 'surfaced' | 'pulled'. Plain Text, no CHECK, like the siblings.
+    event: Mapped[str] = mapped_column(Text, nullable=False)
+    # Which surface produced it — a convention, not a vocabulary (see the
+    # note twin). `grep -rn record_system_ src/` is the authoritative list.
+    source: Mapped[str] = mapped_column(Text, nullable=False)
+    # The project the READER was in, not the System's own.
+    project_id: Mapped[int | None] = mapped_column(BigInteger, nullable=True)
+
+    __table_args__ = (
+        Index("ix_system_usage_system_event", "system_id", "event"),
+        Index("ix_system_usage_created_at", "created_at"),
+    )
+
+    def to_dict(self) -> dict:
+        return {
+            "id": self.id,
+            "created_at": iso(self.created_at),
+            "user_id": self.user_id,
+            "system_id": self.system_id,
+            "event": self.event,
+            "source": self.source,
+            "project_id": self.project_id,
+        }