docs: add service README.md files + update AGENTS.md decisions

- Create README.md for 25+ service modules with container info, API surface, storage
- Document attestor-tileproxy separation rationale (air-gap network isolation)
- Document opsmemory-advisoryai separation rationale (resource isolation, blast radius)
- Update Timeline AGENTS.md with merged indexer info

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/Graph/README.md

@@ -0,0 +1,17 @@
+# Graph
+
+**Container(s):** stellaops-graph-api
+**Slot:** 20  |  **Port:** 8080  |  **Consumer Group:** graph
+**Resource Tier:** medium
+
+## Purpose
+The Graph API service provides a dependency and service graph for the Stella Ops platform. It supports graph search, path queries, diff computation, lineage tracking, overlay projections, saved views, and export functionality. It serves as the central topology store for understanding relationships between components, images, and services.
+
+## API Surface
+- `graph` (via Router) — graph search, path queries, diff, lineage, overlay, saved views, export (GEXF/DOT/JSON), edge metadata, audit log, rate-limited access
+
+## Storage
+PostgreSQL (via `Postgres:Graph` for saved views); in-memory graph repository for core graph data
+
+## Background Workers
+- `GraphSavedViewsMigrationHostedService` — migrates saved views on startup