docs: add missing actor.json properties (meta, title, webServerMcpPath) (#2218)

Fixes #1813
Fixes #1941

## Changes

Added documentation for three properties that were missing from the
actor.json reference:

### 1. `title` property
- **Description**: Display title for the Actor in Apify Console and
Store
- **Type**: Optional
- **Usage**: Human-readable title; falls back to `name` if not specified

### 2. `meta` property  
- **Description**: Metadata object containing additional Actor
information
- **Type**: Optional
- **Current fields**: `templateId` (identifies the template from which
the Actor was created)

### 3. `webServerMcpPath` property
- **Description**: HTTP endpoint path for MCP (Model Context Protocol)
server functionality
- **Type**: Optional
- **Usage**: When set, the Actor is recognized as an MCP server
- **Reference**: [Build and Deploy MCP Servers blog
post](https://blog.apify.com/build-and-deploy-mcp-servers-typescript/)

## What was missing

These properties are already used by:
- Apify platform (for Actor metadata and MCP servers)
- Actor templates (which include `meta.templateId` in generated
`.actor/actor.json` files)

However, they were not documented in the actor.json reference page.

## Updates

- Added all three properties to the reference table
- Updated the full example to show usage of these properties
- Maintained consistency with existing documentation style

## Testing

- [x] All properties documented with clear descriptions
- [x] Example JSON updated to show realistic usage
- [x] Links added where relevant (Standby mode for webServerMcpPath)

---

🤖 Generated with Claude Code

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Documentation-only update that adds reference entries and an example
for existing `actor.json` fields; no runtime or API behavior changes.
> 
> **Overview**
> Updates the `actor.json` docs to include three previously undocumented
properties: **`title`** (human-readable display name),
**`meta.templateId`** (template provenance metadata), and
**`webServerMcpPath`** (marks an Actor web server endpoint as an MCP
interface).
> 
> The full `actor.json` example is expanded to show these fields, and
the reference table is updated with descriptions for each new property.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
268a348. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: marcel-rbro

sources/platform/actors/development/actor_definition/actor_json.md

@@ -23,8 +23,12 @@ import TabItem from '@theme/TabItem';
 {
     "actorSpecification": 1, // always 1
     "name": "name-of-my-scraper",
+    "title": "My Web Scraper",
     "version": "0.0",
     "buildTag": "latest",
+    "meta": {
+        "templateId": "ts-crawlee-playwright-chrome"
+    },
     "defaultMemoryMbytes": "get(input, 'startUrls.length', 1) * 1024",
     "minMemoryMbytes": 256,
     "maxMemoryMbytes": 4096,
@@ -39,7 +43,8 @@ import TabItem from '@theme/TabItem';
     "storages": {
         "dataset": "./dataset_schema.json"
     },
-    "webServerSchema": "./web_server_openapi.json"
+    "webServerSchema": "./web_server_openapi.json",
+    "webServerMcpPath": "/mcp"
 }
 ```
 
@@ -69,8 +74,10 @@ Actor `name`, `version`, `buildTag`, and `environmentVariables` are currently on
 | --- | --- | --- |
 | `actorSpecification` | Required | The version of the Actor specification. This property must be set to `1`, which is the only version available. |
 | `name` | Required | The name of the Actor. |
+| `title` | Optional | The display title of the Actor. This is the human-readable title shown in the Apify Console and Store. If not specified, the `name` property is used as the title. |
 | `version` | Required | The version of the Actor, specified in the format `[Number].[Number]`, e.g., `0.1`, `0.3`, `1.0`, `1.3`, etc. |
 | `buildTag` | Optional | The tag name to be applied to a successful build of the Actor. If not specified, defaults to `latest`. Refer to the [builds](../builds_and_runs/builds.md) for more information. |
+| `meta` | Optional | Metadata object containing additional information about the Actor. Currently supports `templateId` field to identify the template from which the Actor was created. |
 | `environmentVariables` | Optional | A map of environment variables to be used during local development. These variables will also be applied to the Actor when deployed on the Apify platform. For more details, see the [environment variables](/cli/docs/vars) section of Apify CLI documentation. |
 | `dockerfile` | Optional | The path to the Dockerfile to be used for building the Actor on the platform. If not specified, the system will search for Dockerfiles in the `.actor/Dockerfile` and `Dockerfile` paths, in that order. Refer to the [Dockerfile](./docker.md) section for more information. |
 | `dockerContextDir` | Optional | The path to the directory to be used as the Docker context when building the Actor. The path is relative to the location of the `actor.json` file. This property is useful for monorepos containing multiple Actors. Refer to the [Actor monorepos](../deployment/source_types.md#actor-monorepos) section for more details. |
@@ -83,3 +90,4 @@ Actor `name`, `version`, `buildTag`, and `environmentVariables` are currently on
 | `maxMemoryMbytes` | Optional | Specifies the maximum amount of memory in megabytes required by the Actor to run. It can be used to control the costs of run, especially when developing pay per result Actors. Requires an _integer_ value. Refer to the [Usage and resources](https://docs.apify.com/platform/actors/running/usage-and-resources#memory) for more details about memory allocation. |
 | `usesStandbyMode` | Optional | Boolean specifying whether the Actor will have [Standby mode](../programming_interface/actor_standby.md) enabled. |
 | `webServerSchema` | Optional | Defines an OpenAPI v3 schema for the web server running in the Actor. This can be either an embedded object or a path to a JSON schema file. Use this when your Actor starts its own HTTP server and you want to describe its interface. |
+| `webServerMcpPath` | Optional | The HTTP endpoint path where the Actor exposes its MCP (Model Context Protocol) server functionality. When set, the Actor is recognized as an MCP server. For example, setting `"/mcp"` designates the `/mcp` endpoint as the MCP interface. This path becomes part of the Actor's stable URL when [Standby mode](../programming_interface/actor_standby.md) is enabled. |