docs(readme): restructure hero with bullets + tables (#125)

* docs(readme): restructure hero with bullets + tables

Establish a reading rhythm: infra facts as quick bullets, then an
AS CODE table and a Core Use Cases table that unpack each item.

- Feature block → bullets (drop the redundant <br> left on list items).
- AS CODE block → table; "Context as code" reframed around pre-defined,
  versioned queries.
- Use cases → table with one-line unpacking; "Code & dev graph" → "Dev
  graph" (issue + dependency model for AI agents); "Context graph" reframed
  to decision traces + tribal knowledge; "R&D data layer" to experimental
  data written into branches; wiki line to "agent-updatable knowledge base".

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* docs(readme): refine hero copy and lift thesis line

- Promote "operational state & coordination layer for agents" to sit
  directly under the tagline.
- Tighten AS CODE and use-case descriptions.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* docs(readme): make AS CODE rows consistent

Apply the AS CODE motif to all four rows (Security, Dashboards) to match
Schema and Context.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

README.md

@@ -7,27 +7,31 @@
 
 **Lakehouse native graph engine built for context assembly**
 
-Schema AS CODE<br>
-Context AS CODE<br>
-Security AS CODE<br>
-Dashboards AS CODE
+Omnigraph acts as operational state & coordination layer for agents
 
-- Git-style snapshots & branching<br>
-- Object storage native (S3, RustFS)<br>
-- VPC, On-prem, hybrid deployment<br>
+- Git-style snapshots & branching
+- Object storage native (S3, RustFS)
+- VPC, On-prem, hybrid deployment
 - Lance format as storage layer
 
+| AS CODE | |
+|---|---|
+| **Schema AS CODE** | Typed `.pg` schemas, planned, applied, enforced |
+| **Context AS CODE** | Linted queries & agentic nudges, versioned and reusable |
+| **Security AS CODE** | Cedar policies enforced server-side on every mutation |
+| **Dashboards AS CODE** | Declarative views & controls over the graph *(coming)* |
+
 ## Core Use Cases
 
-- Company brain
-- Context graph
-- Agentic memory
-- Code & dev graph
-- R&D data layer
-- ML workflows
-- Karpathy's LLM wiki
-
-Omnigraph acts as operational state & coordination layer for agents
+| Use case | |
+|---|---|
+| **Company brain** | Org knowledge unified into one queryable graph |
+| **Context graph** | Decision traces and codified tribal knowledge |
+| **Agentic memory** | Durable, versioned memory for long-running agents |
+| **Dev graph** | Issues & dependency model for coding agents |
+| **R&D data layer** | Experiments & trials data written into branches |
+| **ML workflows** | Versioned, branchable graphs for training & eval |
+| **Karpathy's LLM wiki** | A living, agent-updatable knowledge base |
 
 ## Quick Install