docs(spring-ai): replace obsolete setup with compatibility warning

[nik13]

Summary

Replace the obsolete Spring AI integration guide with an interim compatibility warning. The historical M4-built traceAI wrapper is not a supported Spring AI 1.1.x setup; NoSuchMethodError involving Message.getContent() has been reported.

• Remove the M4+ support claim, floating main-SNAPSHOT dependency blocks, provider table and obsolete wrapper examples.
• Distinguish the historical compilation target from tested runtime compatibility and a published replacement coordinate.
• Link the versioned Spring AI 1.1 observability and Spring Boot 3.5 tracing references, without promising provider parity or enabling sensitive prompt/completion logging.
• Preserve the canonical page and legacy route mapping.
• Add seven dependency-free source-contract checks.

Verification

Candidate: 968602d59d355d702d3dd6d7fa20232fe543d71d against b61510cba8d6c2576f663fc2f1f5dbb6c9ac529c.

• node --test scripts/spring-ai-warning.test.mjs: seven checks failed on the previous page, then seven passed; independently rerun after implementation.
• npm run build: completed; existing static-redirect/search-index warnings retained.
• npm run audit-links: zero broken navigation/content links; the existing 29 orphan-page notices are unchanged.
• Generated-page assertions passed for the canonical warning and legacy redirect target.
• Actual isolated Chrome local preview: both /docs/integrations/traceai/spring-boot and /docs/tracing/auto/spring-boot reached the canonical warning, with no uncaught JavaScript exceptions. The static preview serves 200 plus a meta refresh; this does not certify deployed HTTP301 behavior.
• Separate source reviewer and independent verifier found no introduced blocking defects. Complete outgoing diff inspected for private/customer content.
• Both versioned official reference URLs were fetched successfully.

Limits

This is a draft documentation-only mitigation, not an SDK repair or release. It does not recommend a replacement artifact or claim a passing Spring AI binary/runtime matrix. The source-contract checks are manually invoked and are not wired into the existing CI workflow. The existing PR Checks / Link audit & redirect enforcement check passed on this candidate (run); this does not certify SDK tests or a required-check branch-protection rule.

Other SDK overview pages still contain pre-existing Spring wrapper references; they are recorded for the compatibility inventory, not silently included in this two-file change. Keep the warning until an immutable published installation has actually been verified.

Video demo

Not attached. This draft is not the final implementation handoff. No merge or deployment is requested.