chore: make dead code a compile error (workspace [lints]) + drop dead index_types

Adds a [workspace.lints] table denying dead_code and unused_imports, with each
member crate opting in via [lints] workspace = true. Dead code is now a hard
`cargo build`/`cargo test` error, not just a clippy -D warnings CI warning, so
an unused fn/field/variant/import cannot rot silently.

Also removes tests/sqlx/src/index_types.rs (and its lib.rs mod + IndexTypes
re-export). The module was a typo-prevention constants scaffold added with the
SQLx test migration (2025-10-27, 47d1c21) but never adopted — all six constants
had zero references since creation. It is the kind of dead code the new lint is
meant to stop, but rustc's dead_code lint exempts unused *pub* items in a lib
crate (it assumes a sibling/downstream crate may use them), and eql_tests is a
lib consumed by its integration tests, so the pub module slipped through. Removed
by hand; the lint guards the private-dead-code case going forward.

Verified: full workspace + every integration test target compiles clean under
the new deny policy; eql-scalars/eql-codegen/eql-tests-macros test suites green.

Author: tobyhede

Cargo.toml

@@ -23,3 +23,9 @@ members = [
     "tests/sqlx",
 ]
 default-members = ["tests/sqlx"]
+
+# Dead code is a hard error. Note: rustc exempts unused `pub` items in a lib, so
+# don't `pub` a test-support item unless an integration test consumes it.
+[workspace.lints.rust]
+dead_code = "deny"
+unused_imports = "deny"

crates/eql-codegen/Cargo.toml

@@ -16,3 +16,6 @@ path = "src/main.rs"
 [lib]
 name = "eql_codegen"
 path = "src/lib.rs"
+
+[lints]
+workspace = true

crates/eql-scalars/Cargo.toml

@@ -8,3 +8,6 @@ description = "Scalar/term catalog for EQL encrypted-domain codegen (std-only, n
 # generator (eql-codegen) compiles in ~1-2s and never drags serde/toml onto the
 # SQL build's critical path. Do not add deps here.
 [dependencies]
+
+[lints]
+workspace = true

crates/eql-tests-macros/Cargo.toml

@@ -12,3 +12,6 @@ syn = { version = "2", features = ["full"] }
 quote = "1"
 proc-macro2 = "1"
 eql-scalars = { path = "../eql-scalars" }
+
+[lints]
+workspace = true

tests/sqlx/Cargo.toml

@@ -23,6 +23,9 @@ eql-tests-macros = { path = "../../crates/eql-tests-macros" }
 [dev-dependencies]
 # None needed - tests live in this crate
 
+[lints]
+workspace = true
+
 [features]
 default = []
 # Opt-in to slow benchmark / regression / scale tests. Without this feature

tests/sqlx/src/index_types.rs

@@ -7,7 +7,6 @@ use sqlx::PgPool;
 pub mod assertions;
 pub mod fixtures;
 pub mod helpers;
-pub mod index_types;
 pub mod matrix;
 pub mod scalar_domains;
 #[macro_use]
@@ -37,7 +36,6 @@ pub use helpers::{
     read_pg_stat_statements, reset_pg_stat_statements, ExplainStats, PgStatEntry,
     PLACEHOLDER_PAYLOAD,
 };
-pub use index_types as IndexTypes;
 pub use scalar_domains::{
     assert_null, assert_raises, assert_scalar_plaintexts, blocker_msg, commute_op,
     fetch_fixture_payload, sql_string_literal, ScalarDomainSpec, ScalarType, Variant,