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/api-reference/dream/dream-preview.mdx

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+---
+title: "Preview Dream Scope"
+description: "A no-write preview of the scope Dream synthesis would analyze for a project."
+openapi: "post /api/v1/orgs/organizations/{org_id}/projects/{project_id}/dream/preview/"
+---

docs/api-reference/dream/get-dream-activity.mdx

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+---
+title: "Get Dream Activity"
+description: "Supersede/merge activity feed for a project, newest first (keyset-paginated)."
+openapi: "get /api/v1/orgs/organizations/{org_id}/projects/{project_id}/dream/activity/"
+---

docs/api-reference/dream/get-dream-config.mdx

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+---
+title: "Get Dream Configuration"
+description: "Retrieve a project's Dream (memory synthesis) configuration and plan entitlements."
+openapi: "get /api/v1/orgs/organizations/{org_id}/projects/{project_id}/dream/config/"
+---

docs/api-reference/dream/get-dream-memory-sources.mdx

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+---
+title: "Get a Synthesized Memory's Sources"
+description: "The source memories a synthesized (pattern) memory was distilled from."
+openapi: "get /api/v1/orgs/organizations/{org_id}/projects/{project_id}/dream/memory/{memory_id}/sources/"
+---

docs/api-reference/dream/get-dream-run-memories.mdx

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+---
+title: "Get Memories in a Dream Run"
+description: "Keyset page of the synthesized memories within a single synthesis run."
+openapi: "get /api/v1/orgs/organizations/{org_id}/projects/{project_id}/dream/runs/{run_id}/memories/"
+---

docs/api-reference/dream/get-dream-runs.mdx

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+---
+title: "Get Dream Synthesis Runs"
+description: "Synthesis activity grouped per run, newest first (keyset-paginated)."
+openapi: "get /api/v1/orgs/organizations/{org_id}/projects/{project_id}/dream/runs/"
+---

docs/api-reference/dream/get-dream-stats.mdx

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+---
+title: "Get Dream Stats"
+description: "Lifecycle and synthesis counts for a project, plus reflection freshness."
+openapi: "get /api/v1/orgs/organizations/{org_id}/projects/{project_id}/dream/stats/"
+---

docs/api-reference/dream/update-dream-config.mdx

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+---
+title: "Update Dream Configuration"
+description: "Enable or disable Synthesis (reflection) for a project, or change the reflection mode."
+openapi: "patch /api/v1/orgs/organizations/{org_id}/projects/{project_id}/dream/config/"
+---