fix: enforce plugin config schemas (#1272) (thanks @thewilloftheshadow)

Co-authored-by: thewilloftheshadow <thewilloftheshadow@users.noreply.github.com>

docs/plugins/manifest.md

@@ -0,0 +1,63 @@
+---
+summary: "Plugin manifest + JSON schema requirements (strict config validation)"
+read_when:
+  - You are building a Clawdbot plugin
+  - You need to ship a plugin config schema or debug plugin validation errors
+---
+# Plugin manifest (clawdbot.plugin.json)
+
+Every plugin **must** ship a `clawdbot.plugin.json` file in the **plugin root**.
+Clawdbot uses this manifest to validate configuration **without executing plugin
+code**. Missing or invalid manifests are treated as plugin errors and block
+config validation.
+
+See the full plugin system guide: [Plugins](/plugin).
+
+## Required fields
+
+```json
+{
+  "id": "voice-call",
+  "configSchema": {
+    "type": "object",
+    "additionalProperties": false,
+    "properties": {}
+  }
+}
+```
+
+Required keys:
+- `id` (string): canonical plugin id.
+- `configSchema` (object): JSON Schema for plugin config (inline).
+
+Optional keys:
+- `kind` (string): plugin kind (example: `"memory"`).
+- `channels` (array): channel ids registered by this plugin (example: `["matrix"]`).
+- `providers` (array): provider ids registered by this plugin.
+- `name` (string): display name for the plugin.
+- `description` (string): short plugin summary.
+- `uiHints` (object): config field labels/placeholders/sensitive flags for UI rendering.
+- `version` (string): plugin version (informational).
+
+## JSON Schema requirements
+
+- **Every plugin must ship a JSON Schema**, even if it accepts no config.
+- An empty schema is acceptable (for example, `{ "type": "object", "additionalProperties": false }`).
+- Schemas are validated at config read/write time, not at runtime.
+
+## Validation behavior
+
+- Unknown `channels.*` keys are **errors**, unless the channel id is declared by
+  a plugin manifest.
+- `plugins.entries.<id>`, `plugins.allow`, `plugins.deny`, and `plugins.slots.*`
+  must reference **discoverable** plugin ids. Unknown ids are **errors**.
+- If a plugin is installed but has a broken or missing manifest or schema,
+  validation fails and Doctor reports the plugin error.
+- If plugin config exists but the plugin is **disabled**, the config is kept and
+  a **warning** is surfaced in Doctor + logs.
+
+## Notes
+
+- The manifest is **required for all plugins**, including local filesystem loads.
+- Runtime still loads the plugin module separately; the manifest is only for
+  discovery + validation.