Feat v0.9.5 typed forms SDK primitive

Extract typed form system from models/workflow.go into standalone
server/forms/ package. Any package can now declare and validate
forms, not just workflow stages.

- New server/forms/ package (types + validation + condition evaluator)
- REST POST /api/v1/forms/validate endpoint
- Starlark forms.validate(template, data) module
- Frontend sw.forms.render(), .validate(), .validateRemote()
- Manifest form_template accepted at package level
- 16 new tests (12 forms + 4 Starlark module)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/API-REFERENCE.md

@@ -184,3 +184,30 @@ Kernel event prefixes: `user.*`, `team.*`, `workflow.*`, `notification.*`, `pres
 | POST | `/presence/heartbeat` | Update presence status |
 | GET | `/presence` | Query online users |
 | GET | `/users/search` | Search users |
+
+### Forms (v0.9.5)
+
+| Method | Path | Description |
+|--------|------|-------------|
+| POST | `/forms/validate` | Validate form data against a typed template |
+
+**Request body:**
+
+```json
+{
+  "template": {
+    "fields": [
+      {"key": "name", "type": "text", "label": "Name", "required": true}
+    ]
+  },
+  "data": {"name": "Alice"}
+}
+```
+
+**Response:**
+
+```json
+{"valid": true, "errors": []}
+```
+
+On validation failure, `errors` contains `[{"key": "name", "message": "Name is required"}]`.