Document v0.6.0 changes in CHANGELOG and docs (#311)

Wrap-up for the v0.6.0 release: capture features/BC breaks merged since
v0.5.0 that were missing from documentation.

- CHANGELOG: add the `title` field on `Resource`/`ResourceTemplate` (#301),
  a feature plus three positional-argument BC breaks.
- mcp-elements.md: add the missing `title` parameter to the McpTool,
  McpResource, McpResourceTemplate and McpPrompt attribute reference
  sections; fix a missing closing paren in an `#[McpPrompt]` example.
- server-builder.md: add `title?` to the `addPrompt()` row of the method
  reference table (stale since v0.5.0).
- client.md: bump the protocol-version example to `V2025_11_25` to match
  the new default.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/client.md

@@ -83,7 +83,7 @@ Specify the MCP protocol version (defaults to latest):
 use Mcp\Schema\Enum\ProtocolVersion;
 
 $client = Client::builder()
-    ->setProtocolVersion(ProtocolVersion::V2025_06_18)
+    ->setProtocolVersion(ProtocolVersion::V2025_11_25)
     ->build();
 ```