feat: rename bugfix-ship/requirement-flow to short-ship/long-ship with shared ship records

short-ship and long-ship share one ship-id record under .pouch/ship/<id>/.
specifier writes PRDs into spec/; delivery-loop appends evidence pointers.
Old names stay as deprecation stubs so existing installs keep working.

skills/ship/templates/current.template.yaml

@@ -0,0 +1,29 @@
+shipId: <ship-id>
+kind: short
+title: <short title>
+status: draft
+stopAt: null
+source:
+  kind: user
+  ref: null
+parentShipId: null
+childShipIds: []
+spec:
+  path: spec.md
+  revision: null
+  specStatus: null
+  prd: null
+  approvedRevision: null
+  reviews: null
+  handoff: null
+tasks:
+  path: tasks.yaml
+delivery:
+  stopAt: null
+  state: change_ready
+evidence:
+  testRuns: []
+  artifacts: []
+  deploys: []
+  prs: []
+  commits: []