docs(api-reference): add Dream (memory synthesis) endpoints

Dream shipped to prod but its API endpoints weren't in the API reference. Add
the org/project-scoped Dream endpoints (OpenAPI spec + per-endpoint pages + nav):

- GET/PATCH dream/config/  — get / update Synthesis config + plan entitlements
- GET  dream/stats/        — lifecycle + synthesis counts
- GET  dream/activity/     — supersede/merge feed (keyset-paginated)
- GET  dream/runs/         — synthesis runs feed
- GET  dream/runs/{run_id}/memories/       — memories within a run
- GET  dream/memory/{memory_id}/sources/   — a synthesized memory's sources
- POST dream/preview/      — no-write scope preview

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/docs.json

@@ -539,6 +539,20 @@
                       "api-reference/project/delete-project"
                     ]
                   },
+                  {
+                    "group": "Dream",
+                    "icon": "sparkles",
+                    "pages": [
+                      "api-reference/dream/get-dream-config",
+                      "api-reference/dream/update-dream-config",
+                      "api-reference/dream/get-dream-stats",
+                      "api-reference/dream/get-dream-activity",
+                      "api-reference/dream/get-dream-runs",
+                      "api-reference/dream/get-dream-run-memories",
+                      "api-reference/dream/get-dream-memory-sources",
+                      "api-reference/dream/dream-preview"
+                    ]
+                  },
                   {
                     "group": "Webhooks",
                     "icon": "webhook",