Summary

spiceai/spiceai#10749 (Arrow primary key upserts) removed the explicit hash_index: enabled parameter from the spicepod schema and changed Arrow acceleration to enable hash indexing automatically when primary_key or indexes is configured. The runtime now logs a warning if hash_index is still set, but the docs at website/docs/features/data-acceleration/hash-index.md continued to instruct users to set hash_index: enabled — which produces a warning and has no effect.

Changes

• Configuration section — rewrote the intro to describe automatic activation, removed hash_index: enabled from both YAML examples, and listed the exact runtime activation conditions.
• Configuration Options table — removed the hash_index row, and added a :::note admonition explaining the deprecation and recommending removal from params.
• Troubleshooting — replaced the obsolete "Add hash_index: enabled to use primary_key" entry with the new "ignored" warning, plus an entry covering the refresh_mode: caching exception that the new runtime logic enforces.

vNext-only: the source change (spiceai/spiceai#10749) is only in trunk / nightly. website/versioned_docs/version-1.11.x/features/data-acceleration/hash-index.md was deliberately left untouched because v1.11.x still requires the explicit hash_index: enabled parameter.

The related references in arrow/index.md, arrow/deployment.md, and partitioning.md are intentionally out of scope for this PR — they'll be addressed in a follow-up. Keeping this PR scoped to the canonical hash-index page makes the review tractable.

Reference

Verified against spiceai/spiceai trunk:

• crates/runtime/src/component/dataset/acceleration.rs lines 357-365 — new is_hash_index_enabled() logic
• crates/runtime/src/component/dataset/acceleration.rs lines 437-441 — ignored-parameter warning text
• crates/runtime/src/component/dataset/acceleration.rs line 745 — test_hash_index_param_is_ignored unit test confirms the runtime behavior

Test plan

• cd website && npm run build passes locally
• No broken links, no undefined tags
• Versioned docs (v1.11.x and earlier) intentionally untouched