docs(lint): backlink R11's doc comment to #8323's measured cross-tenant oracle

lintUnscopedDeclaredIndexes (unique/unscoped-declared-index, R11,
ADR-0120 D5a) already ships the publish-time advisory for the bare
`unique: true` declared-index spelling that materializes a global
unique index. The concrete harm that warning exists to prevent — the
cross-tenant 409-vs-201 oracle — was measured end to end on #8323, but
the connection lived nowhere in the tree, which is why part 3 of the
#8323 ruling was drafted without knowing R11 already delivered its
substance (#8379). One doc-comment line closes that gap for the next
sweep or ruling.

Fixes #8584

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Jqe56GnYFddggeAyfkZFVz

Author: claude

packages/lint/src/data-model-rules.ts

@@ -157,6 +157,8 @@ function indexUniqueScope(u: unknown): 'organization' | 'global' {
  * 17.x: warning. Protocol 18 rejects the spelling at validate/publish (#5082).
  * Advisory — never fails a build in 17.x.
  *
+ * Concrete harm: #8323 measured the cross-tenant 409-vs-201 oracle end to end.
+ *
  * Wiring: own AUTHORING_RULES entry (validate/build), and `lintDataModel`
  * calls it for `os lint` — each command reports each finding exactly once.
  */