Add aggregates.yaml: the full state graph for applicants/subscribers/projects/organizations

Portal's aggregate state machines used to be compiled Rust, duplicated
across four files plus the bucket-name wiring that dispatched to them.
This is now the single source of truth for what states exist, what
event-type string represents each, and what transitions are legal -
portal loads and validates it at boot/reload (see the paired portal
change). Adding a new aggregate, or reshaping an existing one, is now
a content-only change.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

aggregates.yaml

@@ -0,0 +1,47 @@
+# The full state graph for every bucket that wants event-sourced,
+# CAS-protected transitions - see portal's src/aggregates/mod.rs. A
+# bucket with no entry here still works (plain KV mutate-in-place, no
+# event log). `bucket` doubles as both the KV bucket name and the
+# JetStream event-subject segment (events.<bucket>.<id>) - one name,
+# not two.
+#
+# Pages (review.yaml, subscribed.yaml, index.yaml) reference these
+# bucket names and `to:` state names by string; they never re-declare
+# the graph itself. Add a new aggregate here alone - no portal code
+# change needed.
+aggregates:
+  - bucket: applicants
+    initial: open
+    states:
+      open: { event: applied }
+      invited: { event: invited }
+      declined: { event: declined }
+    transitions:
+      open: [invited, declined]
+
+  - bucket: subscribers
+    initial: open
+    states:
+      open: { event: subscribed }
+      unsubscribed: { event: unsubscribed }
+    transitions:
+      open: [unsubscribed]
+
+  - bucket: projects
+    initial: open
+    states:
+      open: { event: submitted }
+      accepted: { event: accepted }
+      declined: { event: declined }
+    transitions:
+      open: [accepted, declined]
+
+  - bucket: organizations
+    initial: prospect
+    states:
+      prospect: { event: identified }
+      client: { event: became_client }
+      past_client: { event: churned }
+    transitions:
+      prospect: [client, past_client]
+      client: [past_client]