docs(sql): document <= comparison operator (Phase 2 checkpoint 3)

Add Doxygen documentation for less-than-or-equal operator:
- lte: Internal comparison helper
- <= operator: Three overloads (encrypted/encrypted, encrypted/jsonb, jsonb/encrypted)

All include @brief, @param, @return tags with example usage.

Part of: add-doxygen-sql-comments plan
Phase: 2 (Core modules - checkpoint 3/7)

Author: tobyhede

src/operators/<=.sql

@@ -2,12 +2,18 @@
 -- REQUIRE: src/encrypted/types.sql
 -- REQUIRE: src/operators/compare.sql
 
-
--- Operators for <= less than or equal to comparisons of eql_v2_encrypted types
---
--- Uses `eql_v2.compare` for the actual comparison logic.
---
---
+--! @brief Less-than-or-equal comparison helper for encrypted values
+--! @internal
+--!
+--! Internal helper that delegates to eql_v2.compare for <= testing.
+--! Returns true if first value is less than or equal to second using ORE comparison.
+--!
+--! @param a eql_v2_encrypted First encrypted value
+--! @param b eql_v2_encrypted Second encrypted value
+--! @return Boolean True if a <= b (compare result <= 0)
+--!
+--! @see eql_v2.compare
+--! @see eql_v2."<="
 CREATE FUNCTION eql_v2.lte(a eql_v2_encrypted, b eql_v2_encrypted)
   RETURNS boolean
 AS $$
@@ -16,8 +22,21 @@ AS $$
   END;
 $$ LANGUAGE plpgsql;
 
-
-
+--! @brief Less-than-or-equal operator for encrypted values
+--!
+--! Implements the <= operator for comparing encrypted values using ORE index terms.
+--! Enables range queries with inclusive lower bounds without decryption.
+--!
+--! @param a eql_v2_encrypted Left operand
+--! @param b eql_v2_encrypted Right operand
+--! @return Boolean True if a <= b
+--!
+--! @example
+--! -- Find records with encrypted age 18 or under
+--! SELECT * FROM users WHERE encrypted_age <= '18'::int::text::eql_v2_encrypted;
+--!
+--! @see eql_v2.compare
+--! @see eql_v2.add_search_config
 CREATE FUNCTION eql_v2."<="(a eql_v2_encrypted, b eql_v2_encrypted)
 RETURNS boolean
 AS $$
@@ -36,8 +55,8 @@ CREATE OPERATOR <=(
   JOIN = scalarltjoinsel
 );
 
-
-
+--! @brief <= operator for encrypted value and JSONB
+--! @see eql_v2."<="(eql_v2_encrypted, eql_v2_encrypted)
 CREATE FUNCTION eql_v2."<="(a eql_v2_encrypted, b jsonb)
 RETURNS boolean
 AS $$
@@ -56,8 +75,8 @@ CREATE OPERATOR <=(
   JOIN = scalarltjoinsel
 );
 
-
-
+--! @brief <= operator for JSONB and encrypted value
+--! @see eql_v2."<="(eql_v2_encrypted, eql_v2_encrypted)
 CREATE FUNCTION eql_v2."<="(a jsonb, b eql_v2_encrypted)
 RETURNS boolean
 AS $$