docs: update all docs/conventions for stateful sense, remove stale refs

Phase 4 of RFC #308: Stateful Sense refactor.

- CLAUDE.md: updated diagram, tables, examples (no more Signal)
- Cleaned stale Signal Bus / DrizzleDB / _signals / retention refs
  across READMEs, .cursor rules, copilot instructions, .knowledge
- Removed drizzle-orm from core package.json (no longer used)
- Updated pnpm-lock.yaml

Refs #308

.github/copilot-instructions.md

@@ -3,7 +3,7 @@
 ## Core Concepts
 
 ```
-External World → Sense → Signal → Reflex → Workflow → Log
+External World → Sense(state) → { newState, workflow? } → Workflow → Log
                   ↑                                     ↑
               "what to observe"                  "what to do"
 ```
@@ -14,19 +14,17 @@ External World → Sense → Signal → Reflex → Workflow → Log
 
 | Concept | What it is |
 |---------|-----------|
-| **Sense** | A `compute()` function that samples or derives data. Returns `T \| null` — non-null emits a Signal, null is silent. Each Sense has its own SQLite database. |
-| **Signal** | A notification emitted when a Sense returns non-null. Pure fact, no intent. Distributed via an in-memory Signal Bus. Not persisted. |
-| **Reflex** | A declarative trigger (YAML) connecting Senses to actions. Trigger types: `interval` (periodic), `on` (react to Signals). Action types: trigger a Sense, or start a Workflow. |
+| **Sense** | A stateful `compute(state)` function. Returns new state and an optional workflow trigger. State persisted as JSON. Scheduling (`interval`, `on`) is configured per sense in nerve.yaml. |
 | **Workflow** | A stateful multi-step execution. Contains **Roles** (actors with side effects) and a **Moderator** (pure router). Each instance is a **Thread** with a unique `runId`. |
-| **Log** | Immutable audit trail. Records executions, state transitions, errors. **Cannot trigger Reflexes** — prevents feedback loops. |
-| **Engine** | The kernel orchestrating everything. Holds Signal Bus, Reflex Scheduler, Process Manager, Workflow Manager. Never loads user code directly — all user code runs in isolated Workers. |
+| **Log** | Immutable audit trail. Records executions, state transitions, errors. **Cannot trigger senses or workflows** — prevents feedback loops. |
+| **Engine** | The kernel orchestrating everything. Holds Process Manager, Workflow Manager, Sense Scheduler. Never loads user code directly — all user code runs in isolated Workers. |
 | **Daemon** | The `nerve-daemon` package — engine runtime. Runs as a background process. |
 
 ### Architecture Rules
 
-- **Three orthogonal extension points**: Sense (what to compute), Reflex (when to compute), Workflow (what to do)
+- **Two orthogonal extension points**: Sense (what to observe + when), Workflow (what to do)
 - **Process isolation**: One worker per Sense group (long-lived), one per Workflow type (on-demand). Workers never talk to each other.
-- **Causality is one-directional**: External world → Sense → Signal → Reflex → Action + Log. Logs are the end of the chain.
+- **Causality is one-directional**: External world → Sense(state) → Workflow (when triggered) + Log. Logs are the end of the chain.
 
 
 
@@ -38,18 +36,18 @@ Use `function` + `type`, not `class` + `interface`.
 
 ```typescript
 // ✅ Good
-type Signal = {
-  senseId: string;
-  value: unknown;
+type WorkflowLaunch = {
+  senseName: string;
+  workflowName: string;
   ts: number;
 };
 
-function createSignal(senseId: string, value: unknown): Signal {
-  return { senseId, value, ts: Date.now() };
+function recordWorkflowLaunch(senseName: string, workflowName: string): WorkflowLaunch {
+  return { senseName, workflowName, ts: Date.now() };
 }
 
 // ❌ Bad — no class, no interface
-class Signal implements ISignal { ... }
+class WorkflowLaunch implements IWorkflowLaunch { ... }
 ```
 
 ### Rules
@@ -94,9 +92,9 @@ For mutually exclusive fields, use discriminated unions:
 
 ```typescript
 // ✅ Good
-type ReflexConfig =
-  | { kind: "sense"; sense: string; interval: string | null; on: string[] | null }
-  | { kind: "workflow"; workflow: string; on: string[] | null };
+type WorkflowConfig =
+  | { concurrency: number; overflow: "drop" }
+  | { concurrency: number; overflow: "queue"; maxQueue: number };
 ```
 
 ## Modules & Exports
@@ -108,9 +106,9 @@ type ReflexConfig =
 
 | Type | Style | Example |
 |------|-------|---------|
-| Files | kebab-case | `signal-bus.ts` |
-| Types | PascalCase | `SignalBus` |
-| Functions/variables | camelCase | `createSignalBus` |
+| Files | kebab-case | `sense-scheduler.ts` |
+| Types | PascalCase | `SenseScheduler` |
+| Functions/variables | camelCase | `createSenseScheduler` |
 | Constants | UPPER_SNAKE | `MAX_RETRY_COUNT` |
 | Generics | Single letter or descriptive | `T`, `TValue` |