docs(runtime): cite the real test file in the share-link mirror docblock

The mirror's docblock told the next reader that the two spellings of
`isPublicSharingEnabled` are held equal by pins in
`share-links-probe-policy-gate.test.ts`. `git ls-tree -r` has zero entries
for that name anywhere in the repo — the pins are in
`share-links-enforcement-context.test.ts`, in this same directory.

This lands on the change's own thesis: a security property stated in a
comment is worth having only if the next reader can follow the comment to
the thing that holds it. A citation to a file that does not exist is the
same defect class the gate itself closes, one layer up.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AUF1NoViznQK32gqpK8wS8

Author: claude

packages/runtime/src/domains/share-links.ts

@@ -49,7 +49,7 @@ import type { DomainHandlerDeps, DomainRoute } from '../domain-handler-registry.
  * than imported because `@objectstack/plugin-sharing` is a **dev** dependency
  * of this package: importing it here would invert the dependency direction to
  * make one boolean read shared. The two spellings are held equal by the pins
- * in `share-links-probe-policy-gate.test.ts` on this side and
+ * in `share-links-enforcement-context.test.ts` on this side and
  * `share-link-eligibility.test.ts` on the other, which assert the SAME
  * observable answer on both surfaces rather than trusting the copy.
  *