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/mcp/tools/systems.py

@@ -18,6 +18,7 @@ from scribe.services import canonical_systems as canonical_systems_svc
 from scribe.services import milestones as milestones_svc
 from scribe.services import notes as notes_svc
 from scribe.services import systems as systems_svc
+from scribe.services.system_usage import record_system_pulled
 
 # Below this, a project is young enough that the mild "which area is this
 # about?" question stays proportionate; at or above it, a zero-Systems project
@@ -293,6 +294,9 @@ async def get_system(system_id: int) -> dict:
     system = await systems_svc.get_system(uid, system_id)
     if system is None:
         raise ValueError(f"system {system_id} not found")
+    # The pull half of the rulings arm's measurement (milestone 444): a
+    # System whose rulings were shown, then opened.
+    record_system_pulled(user_id=uid, system_id=system_id, source="mcp_get_system")
     records = await systems_svc.list_records_for_system(uid, system_id)
     titles = await milestones_svc.titles_for({r.milestone_id for r in records})
     issues, tasks, notes = [], [], []