Merge v2 review fixes (placeholder pages, non-permanent redirects)

# Conflicts:
#	v2-redirects.mjs

Author: coderdan

IA.md

@@ -17,7 +17,7 @@ on a product decision (see CIP-3307 checklist).
   enforces that every legacy page has a mapping.
 - Frontmatter facets (`type`, `components`, `audience`, `integration`,
   `verifiedAgainst`, `reviewBy`) are defined in `source.config.ts` (`v2docs`).
-- **Moving a page = ** move the file into `content/docs`, update its facets,
+- **Moving a page** = move the file into `content/docs`, update its facets,
   fix inbound links, confirm its `v2-redirects.mjs` entry, tick it here.
 
 ## URL conventions

content/docs/concepts/searchable-encryption.mdx

@@ -0,0 +1,9 @@
+---
+title: Searchable encryption
+description: "How querying encrypted data works, and exactly what each index term reveals."
+type: concept
+---
+
+This page is being rewritten as part of the docs V2 overhaul ([CIP-3333](https://linear.app/cipherstash/issue/CIP-3333)). Track progress in [IA.md](https://github.com/cipherstash/docs/blob/v2/IA.md).
+
+Until it lands, the current version lives in the [existing docs](/stack/cipherstash/encryption/searchable-encryption).

content/docs/guides/troubleshooting/query-performance.mdx

@@ -0,0 +1,9 @@
+---
+title: Query performance
+description: "Diagnosing and fixing slow queries on encrypted columns."
+type: guide
+---
+
+This page is being built as part of the docs V2 overhaul ([CIP-3351](https://linear.app/cipherstash/issue/CIP-3351)). Track progress in [IA.md](https://github.com/cipherstash/docs/blob/v2/IA.md).
+
+Until it lands, the EQL reference covers the essentials: [Indexes](/reference/eql/indexes) walks through `EXPLAIN` verification and large-table index builds, and [Sorting](/reference/eql/sorting) covers extractor-form sort keys.