Propagate @McpResource title to generated resources

[alpin87]

Fixes #6786

Background — @McpResource(title = "...") never reached the client. MCP clients then fall back to name, which defaults to the Java method name, so a server author who sets a title sees no effect and no error.

Cause — The four resource providers build McpSchema.Resource / ResourceTemplate without ever reading McpResource#title:

var mcpResource = McpSchema.Resource.builder(uri, name)
    .description(description)
    .mimeType(mimeType)
    .meta(meta)
    .build();               // no .title(...)

These are the runtime path — SyncMcpAnnotationProviders and AsyncMcpAnnotationProviders delegate to them. ResourceAdapter#asResource does set the title, but nothing in production calls that adapter. @McpTool and @McpPrompt both propagate their title, so resources were the only family dropping it.

Fix — Set the title in all four providers, for both the resource and the resource-template paths (8 sites). It is applied only when it has text, so resources without a title keep serializing exactly as before rather than gaining an empty title: "".

I deliberately kept this narrow. Routing the providers through ResourceAdapter would fix #6749 at the same time, but that pulls in the lastModified design question raised there which has no maintainer answer yet. Happy to do it that way instead if you prefer — just say so.

Validation

Added three tests to each of the four provider test classes: title propagated on a resource, title propagated on a resource template, and title absent when unset.

Verified they actually catch the bug by reverting the main-code change and re-running — 8 failures, 2 per provider:

expected: "My Resource Title"
 but was: null

With the fix applied:

$ ./mvnw -pl mcp/mcp-annotations -am -Dtest='*ResourceProviderTests' test
Tests run: 21, Failures: 0, Errors: 0, Skipped: 0 -- SyncMcpResourceProviderTests
Tests run: 19, Failures: 0, Errors: 0, Skipped: 0 -- AsyncMcpResourceProviderTests
Tests run: 18, Failures: 0, Errors: 0, Skipped: 0 -- SyncStatelessMcpResourceProviderTests
Tests run: 19, Failures: 0, Errors: 0, Skipped: 0 -- AsyncStatelessMcpResourceProviderTests
Tests run: 77, Failures: 0, Errors: 0, Skipped: 0
BUILD SUCCESS

Checkstyle passes. The commit is signed off per the DCO.