feat(mcp): expose DICE tools for MCP server integration

[LordKay-sudo]

Summary

• Add DiceMcpTools with simplified context_id-scoped parameters for external MCP clients (Claude Desktop, Cursor, etc.).
• Add dice-mcp-autoconfigure to export tools via embabel-agent McpToolExport when embabel.dice.mcp.enabled=true.
• Support core (4 tools) and extended profiles; optional extraction/entity tools export only when the host app wires the corresponding beans.

Fixes #5

Motivation

Issue #5 asks to make it easy to expose DICE over MCP. External clients are stateless, so every tool takes an explicit context_id, same idea as #6's context-scoped chunk history.

#49 added DiscoveryTools and GraphQueryTools with manual asTools() registration. This PR closes the remaining gap: auto-wiring McpToolExport + embabel-agent-starter-mcpserver so a Spring Boot app can expose DICE over MCP without bespoke configuration.

Scope

This only exports DiceMcpTools (recall, list, store, get, plus extract/assert when wired). DiscoveryTools and GraphQueryTools from #49 are a separate surface. Those bake context in at construction for in-process agents, so I left them out of the MCP autoconfig path. Happy to follow up if discovery/graph tools over MCP are wanted.

What changed

Area	Change
com.embabel.dice.mcp	DiceMcpTools, DiceMcpProfile, DiceMcpSupport
dice-mcp-autoconfigure	Opt-in Spring Boot wiring + named diceMcpToolExport bean
Docs	README MCP section, AGENTS.md navigation

Test plan

• DiceMcpToolsTest - store/get, recall, context isolation, profiles, optional-tool guards
• mvn test -pl dice,dice-mcp-autoconfigure
• full mvn test verify on CI after rebase onto main