stash-prisma skill: functional-index guidance is stale on Prisma Next 0.17 #895

Problem

skills/stash-prisma/SKILL.md ("Indexing encrypted columns") states:

schema.prisma cannot express functional indexes (@@index takes fields, not expressions), so the schema file is not an option.

and prescribes hand-written rawSql migration operations as the only way to create the eql_v3.* functional indexes.

This was true on 0.16 but is false on Prisma Next 0.17 (the surface #749 just moved us to). Verified against the installed @prisma/orm-family-sql@0.17.0 dist:

• PSL @@index accepts named args expression, where, unique, name/map, type, options, with validation (expression XOR fields; an expression index requires name or map; options requires type).
• The TS contract builder's index() accepts the {expression, ...} form.
• target-postgres renders CREATE [UNIQUE] INDEX ... USING <type> (<expression>) WITH (...) WHERE (...) (pgRenderCreateIndex).

So a user can write, directly in schema.prisma:

@@index(expression: "eql_v3.eq_term(email)", name: "users_email_eq", type: "btree")
@@index(expression: "eql_v3.match_term(bio)", name: "users_bio_match", type: "gin")

Fix

• Rewrite the "Indexing encrypted columns" section around the @@index(expression:) form as the primary recipe; keep rawSql as the fallback and the home of ANALYZE.
• Check skills/stash-indexing/SKILL.md for the same claim / cross-references.
• Skills ship in the stash tarball → needs a stash patch changeset.

Auto-generating these indexes from the codec (no user-authored index at all) is the larger follow-up, tracked separately.