[spring ai] add overall support for Spring AI

[martinlippert]

Certain aspects of Spring AI are probably good candidates to implement specific support for:

• index @Tool and @McpTool annotations, so that they show up as symbols and child elements

Additional thoughts to investigate:

• visualize the models that are configured/used
• provide auto-completion / validation for model IDs
• a skill for the latest Spring AI version (from the documentation), so that the AI coding assistant provides meaningful Spring AI code
• probably more...