feat(systems): the area vocabulary becomes a global table so a rule can point at one (#3027, milestone 307 step 1)

The eight standard area names already existed — as STANDARD_SYSTEMS, a tuple in
services/systems.py that milestone 297 seeds at inception. A constant cannot be
a foreign key, so nothing outside a project could reference an area: systems.
project_id is NOT NULL, and a rule that spans projects would have to chain
itself to one project's row. And because the list only ever applied on the
inception-seed path, three spellings of one area reached this instance anyway
(CI & runners / CI and Release / CI & release).

- canonical_systems: global, no user_id — a shared project inherits the
  vocabulary instead of re-earning it. Migration 0087 seeds the same eight.
- systems.canonical_id: nullable, SET NULL. Association only — no System is
  renamed and record_systems is untouched, so no record's tags move.
- canonical_slug folds &/and, case and punctuation, so spelling variants map
  mechanically and a real difference ("CI & runners") becomes a proposal a
  human confirms. propose_mappings reports; set_system_canonical is the only
  writer.
- seed_standard_systems now reads the catalog and maps as it mints, so a
  project born standard never needs a reconciliation pass.
- Catalog writes are admin-only; reads are open — a global list anyone can
  extend stops being shared.
- backup: carried by SLUG, not id (ids are per-install). Restore reuses the
  target's own rows and only creates entries an admin added on the source; an
  unknown slug restores unmapped rather than failing.

Rule 22: STANDARD_SYSTEMS is removed, not deprecated. Rule 115: nothing seeded
names an app, repo or house convention. Design in note 3026.

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

alembic/versions/0087_canonical_systems.py

@@ -0,0 +1,109 @@
+"""canonical_systems — the global area vocabulary, promoted from a constant
+to a table (milestone 307 step 1, decision note 3026)
+
+Revision ID: 0087
+Revises: 0086
+Create Date: 2026-08-26
+
+The eight standard area names already existed as `STANDARD_SYSTEMS`, a tuple in
+services/systems.py that milestone 297 seeds into a project at inception. A
+constant cannot be referenced: a rule that applies across projects has nothing
+to point at, because `systems.project_id` is NOT NULL and a family rule cannot
+be chained to one project's row. This makes the vocabulary a table so it can be
+a foreign key, and adds the nullable `systems.canonical_id` that maps a
+project's local System onto it.
+
+Deliberately no `user_id`: the catalog is GLOBAL so a shared project inherits
+the vocabulary rather than re-earning it. `record_systems` is untouched — it
+joins note_id/system_id and never sees this table, so no association data
+moves, and no System's own `name` is rewritten.
+
+The seed rows are written here verbatim rather than imported from the service:
+a migration is a historical record and must keep running unchanged after the
+service's list moves on.
+"""
+import sqlalchemy as sa
+from alembic import op
+
+revision = "0087"
+down_revision = "0086"
+branch_labels = None
+depends_on = None
+
+
+# (name, slug, description) — the milestone-297 vocabulary, with the slug the
+# service computes (canonical_slug: lowercase, "&" -> "and", non-alphanumerics
+# collapsed to "-"). Charters stay generic on purpose: a project refines its
+# own System's description, never this one. Nothing here names an app, a repo,
+# a vendor or a house convention — the catalog ships to every install (rule 115).
+_SEED = (
+    ("CI & Release", "ci-and-release",
+     "How the project is verified and shipped: pipelines, runners, image/artifact builds, release tagging and rollback."),
+    ("Auth & Access", "auth-and-access",
+     "Who may do what: identity, sessions/tokens, permissions and the scoping of every read and write to the right users."),
+    ("Data Model & Storage", "data-model-and-storage",
+     "What is stored and how it is shaped: the schema, migrations, serialisation and the services that own a table's lifecycle."),
+    ("API Surface", "api-surface",
+     "The doors into the capability: HTTP routes, tool/RPC surfaces, request parsing, error envelopes and their contracts."),
+    ("UI & Design", "ui-and-design",
+     "What people see and touch: views, components, client state, and the design tokens/recipes they are built from."),
+    ("Import & Export", "import-and-export",
+     "Data crossing the boundary: backups, exports, imports, sync with other systems, file formats."),
+    ("Background Jobs", "background-jobs",
+     "Work that runs without a request: schedulers, queues, periodic ticks, retention and maintenance."),
+    ("Observability", "observability",
+     "How the system reports on itself: logging, metrics, audit trails, health and diagnostics."),
+)
+
+
+def upgrade() -> None:
+    canonical_systems = op.create_table(
+        "canonical_systems",
+        sa.Column("id", sa.Integer(), primary_key=True),
+        sa.Column("name", sa.Text(), nullable=False),
+        sa.Column("slug", sa.Text(), nullable=False),
+        sa.Column("description", sa.Text(), nullable=True),
+        sa.Column("order_index", sa.Integer(), nullable=False, server_default="0"),
+        sa.Column("created_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.text("now()")),
+        sa.Column("updated_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.text("now()")),
+        sa.Column("deleted_at", sa.DateTime(timezone=True), nullable=True),
+        sa.Column("deleted_batch_id", sa.Text(), nullable=True),
+    )
+    # Unique among LIVE rows only, so a soft-deleted entry doesn't block
+    # recreating or restoring the same area (the rules/topics convention).
+    op.create_index(
+        "uq_canonical_systems_slug", "canonical_systems", ["slug"],
+        unique=True, postgresql_where=sa.text("deleted_at IS NULL"),
+    )
+    op.bulk_insert(
+        canonical_systems,
+        [
+            {"name": name, "slug": slug, "description": description, "order_index": index}
+            for index, (name, slug, description) in enumerate(_SEED)
+        ],
+    )
+
+    op.add_column(
+        "systems",
+        sa.Column("canonical_id", sa.Integer(), nullable=True),
+    )
+    # SET NULL, not CASCADE: retiring a catalog entry must never delete a
+    # project's System along with it.
+    op.create_foreign_key(
+        "fk_systems_canonical_id", "systems", "canonical_systems",
+        ["canonical_id"], ["id"], ondelete="SET NULL",
+    )
+    op.create_index("ix_systems_canonical_id", "systems", ["canonical_id"])
+
+    # Existing Systems are left UNMAPPED on purpose. An exact-slug match would
+    # be safe, but a near miss ("CI & runners" vs "CI & Release") is a judgment
+    # call — those go through the propose/confirm path so a human approves each
+    # one, rather than being decided by a migration nobody reviews.
+
+
+def downgrade() -> None:
+    op.drop_index("ix_systems_canonical_id", table_name="systems")
+    op.drop_constraint("fk_systems_canonical_id", "systems", type_="foreignkey")
+    op.drop_column("systems", "canonical_id")
+    op.drop_index("uq_canonical_systems_slug", table_name="canonical_systems")
+    op.drop_table("canonical_systems")