docs: rewrite README — philosophy, three-layer model, Agent-in-the-Loop

小橘 🍊（NEKO Team）

README.md

@@ -1,37 +1,72 @@
 # OGraph
 
-**Event Sourcing + Projection + Reaction engine on Cloudflare Workers.**
+**Event Sourcing + Projection + Reaction engine for Agent ecosystems.**
 
 Part of the [Uncaged](https://github.com/oc-xiaoju/uncaged) ecosystem.
 
+## Philosophy
+
+1. **Event is fact** — immutable, append-only, no logic
+2. **Projection is cache** — lazy, closed-world, on-demand computation
+3. **Intelligence lives in the Agent, not the Engine** — Agent-in-the-Loop
+
+### Why not Kafka?
+
+| | Kafka | OGraph |
+|---|---|---|
+| Metaphor | Ballistic missile (design, fire) | Guided missile (adjust in flight) |
+| Pipeline | Pre-defined by humans | Agent defines/adjusts at runtime |
+| Computation | Eager (continuous update) | **Lazy** (on-demand) |
+| JOIN | ✅ KTable synchronized | ❌ Projections are independently lazy |
+| Aggregation | Pre-set materialized views | Actor (Agent) assembles in real-time |
+| Core assumption | Humans design everything upfront | **Agent-in-the-Loop: runtime decisions** |
+
+Traditional Event Sourcing (Kafka, EventStoreDB) assumes pipelines are designed, deployed, and maintained by human developers. OGraph assumes an Agent with decision-making capability dynamically defines Projections, adjusts Watch lists, and assembles aggregations at runtime.
+
+This is not a feature trade-off. It's a paradigm difference.
+
+### Lazy Update — a logical necessity
+
+1. Agent can define new Projections at any time → can't assume all Projections are deployed
+2. → Must be Lazy (compute on demand)
+3. → No consistent cross-Projection snapshot → abandon JOIN
+
+Each step is logically inevitable. From a single assumption — "Agent defines Projections at runtime" — the entire computation model follows.
+
+## Three-Layer Modeling
+
+### Layer 1: Event — Facts
+Immutable records of what happened. No judgment, no derived logic.
+
+### Layer 2: Projection — Cache
+Deterministic computation over event streams. Core constraint: **computational closure** — expression inputs are only `$state`, `$event`, `$params`. Cannot query other Projections or make external calls.
+
+### Layer 3: Actor — Behavior
+Observes multiple Projections, executes complex logic and side effects. Watch lists are **dynamic** — derived from data, not hardcoded.
+
 ## Packages
 
 | Package | Description | npm |
 |---|---|---|
 | [`@uncaged/ograph`](packages/engine/) | CF Worker engine — events, projections, reactions | [![npm](https://img.shields.io/npm/v/@uncaged/ograph)](https://www.npmjs.com/package/@uncaged/ograph) |
 | [`@uncaged/ograph-cli`](packages/cli/) | CLI for managing OGraph instances | [![npm](https://img.shields.io/npm/v/@uncaged/ograph-cli)](https://www.npmjs.com/package/@uncaged/ograph-cli) |
-
-## Core Concepts
-
-- **Event** — Immutable facts with typed properties and object references
-- **Projection** — Derived state computed incrementally from events via reducers
-- **Reaction** — Side effects triggered by projection state changes (webhooks, event emission, handlers)
+| [`@uncaged/ograph-dispatcher`](packages/dispatcher/) | Local daemon — polls projections, notifies Agent when idle | |
 
 ## Quick Start
 
 ```bash
 npm install -g @uncaged/ograph-cli
 ograph deploy          # Deploy to Cloudflare Workers
-ograph event-def add   # Define event types
-ograph event add       # Emit events
-ograph projection list # Query projections
+ograph event-defs list # List event types
+ograph events emit     # Emit events
+ograph schema          # View all definitions
 ```
 
 ## Development
 
 ```bash
 npm install
-npm test              # Run all tests
+npm test              # Run all tests (163+)
 cd packages/engine && npm run dev  # Local dev server
 ```
 
@@ -39,8 +74,11 @@ cd packages/engine && npm run dev  # Local dev server
 
 - **D1** for storage (events, projections, reactions)
 - **Hono** for API routing
-- **Incremental reduce** — projections track `last_event_id` for O(delta) updates
+- **Lazy incremental reduce** — projections track `last_event_id` for O(delta) updates
+- **Projection health** — errored projections stop updating, auto-recover when fixed
 - **Dynamic handlers** — `new Function()` sandboxed execution with emit/log/kv API injection
+- **API Key** — `ogk_` prefix, SHA-256 hash, event type whitelist
+- **Structured errors** — `{ error: { code, message } }`
 
 ## License