docs(PRD): remove hardcoded instance URLs — plugin must be user-configured

No hardcoded brain.woltje.com or any specific host.
baseUrl + apiKey required; missing = OpenBrainConfigError at bootstrap.

docs/PRD.md

@@ -7,7 +7,7 @@
 
 ## Problem Statement
 
-OpenClaw compacts context when sessions grow long, causing information loss. The new `ContextEngine` plugin interface (merged in PR #22201) allows replacing the default compaction strategy with a persistent, lossless alternative. OpenBrain (brain.woltje.com) is a live pgvector + REST API service that can store and semantically retrieve conversation context indefinitely.
+OpenClaw compacts context when sessions grow long, causing information loss. The new `ContextEngine` plugin interface (merged in PR #22201) allows replacing the default compaction strategy with a persistent, lossless alternative. OpenBrain is a self-hosted pgvector + REST API service that can store and semantically retrieve conversation context indefinitely.
 
 ## Solution
 
@@ -20,8 +20,8 @@ lossless-claw (https://github.com/Martian-Engineering/lossless-claw) is the prim
 ## OpenBrain API
 
 ```
-Base: https://brain.woltje.com
-Auth: Bearer <OPENBRAIN_API_KEY>
+Base: <user-configured — OPENBRAIN_URL env var or plugin config.baseUrl — NO DEFAULT>
+Auth: Bearer <OPENBRAIN_API_KEY env var or plugin config.apiKey — NO DEFAULT>
 
 POST   /v1/thoughts         { content, source, metadata }
 POST   /v1/search           { query, limit }
@@ -85,8 +85,8 @@ export function register(api: OpenClawPluginApi) {
       "openclaw-openbrain-context": {
         "enabled": true,
         "config": {
-          "baseUrl": "https://brain.woltje.com",
-          "apiKey": "${OPENBRAIN_API_KEY}",
+          "baseUrl": "https://your-openbrain-instance.example.com",
+          "apiKey": "your-api-key",
           "recentMessages": 20,
           "semanticSearchLimit": 10,
           "source": "openclaw"
@@ -103,15 +103,27 @@ export function register(api: OpenClawPluginApi) {
 - openclaw/plugin-sdk for ContextEngine interface
 - pnpm, vitest, ESLint
 
+## ⚠️ Hard Rule: No Hardcoded Instance Values
+
+This plugin will be used by anyone running their own OpenBrain instance. The following are STRICTLY FORBIDDEN in source code, defaults, or fallback logic:
+- Any hardcoded URL (no `brain.woltje.com` or any other specific domain)
+- Any hardcoded API key
+- Any `process.env.OPENBRAIN_URL || 'https://brain.woltje.com'` fallback patterns
+
+Required behavior:
+- `baseUrl` and `apiKey` MUST be provided via plugin config or env vars
+- If either is missing, throw `OpenBrainConfigError` at `bootstrap()` time with a clear message: "openclaw-openbrain-context: baseUrl and apiKey are required. Set them in your openclaw.json plugin config."
+- No silent degradation, no defaults to any specific host
+
 ## Acceptance Criteria (v0.0.1)
 1. Plugin registers as a ContextEngine with id `openbrain`
 2. `ingest()` stores messages to OpenBrain with correct metadata
 3. `assemble()` retrieves recent + semantically relevant context within token budget
 4. `compact()` archives turn summary, returns minimal prompt-injection
-5. `bootstrap()` loads prior session context on restart
+5. `bootstrap()` loads prior session context on restart; throws `OpenBrainConfigError` if config missing
 6. Tests pass, TypeScript strict, ESLint clean
 7. openclaw.plugin.json with correct manifest
-8. README: install + config + usage
+8. README documents: self-host OpenBrain setup, all config options with types/defaults, env var pattern, example config
 
 ## ASSUMPTION: ContextEngine interface shape
 Based on lossless-claw source and PR #22201. Plugin SDK import path: `openclaw/plugin-sdk`.