test: add golden conformance suite with cross-format fixtures

* feat: add golden conformance test suite for format conversion and mappings

Adds 14 golden-file tests that detect output drift across parsers,
serializers, and the mapping evaluator:

- 7 format conversion tests (JSON/CSV/YAML cross-product)
- 4 mapping tests (rename, select, filter, complex pipeline)
- 3 round-trip consistency tests (JSON↔YAML, JSON↔CSV, YAML↔CSV)

Golden files can be updated with: UPDATE_GOLDEN=1 cargo test --test golden_conformance

Fixes #82

* fix: normalize line endings in golden tests for Windows compatibility

Author: alvinreal

tests/golden/expected/csv_to_json.txt

@@ -0,0 +1,23 @@
+[
+  {
+    "id": 1,
+    "name": "Alice",
+    "email": "alice@example.com",
+    "age": 30,
+    "active": true
+  },
+  {
+    "id": 2,
+    "name": "Bob",
+    "email": "bob@example.com",
+    "age": 25,
+    "active": false
+  },
+  {
+    "id": 3,
+    "name": "Charlie",
+    "email": "charlie@example.com",
+    "age": 35,
+    "active": true
+  }
+]

tests/golden/expected/csv_to_yaml.txt

@@ -0,0 +1,15 @@
+- id: 1
+  name: Alice
+  email: alice@example.com
+  age: 30
+  active: true
+- id: 2
+  name: Bob
+  email: bob@example.com
+  age: 25
+  active: false
+- id: 3
+  name: Charlie
+  email: charlie@example.com
+  age: 35
+  active: true

tests/golden/expected/json_complex_mapping.txt

@@ -0,0 +1,3 @@
+{
+  "email_domain": "example.com"
+}

tests/golden/expected/json_filter_mapping.txt

@@ -0,0 +1,16 @@
+[
+  {
+    "id": 1,
+    "name": "Alice",
+    "email": "alice@example.com",
+    "age": 30,
+    "active": true
+  },
+  {
+    "id": 3,
+    "name": "Charlie",
+    "email": "charlie@example.com",
+    "age": 35,
+    "active": true
+  }
+]

tests/golden/expected/json_rename_mapping.txt

@@ -0,0 +1,23 @@
+[
+  {
+    "id": 1,
+    "name": "Alice",
+    "email": "alice@example.com",
+    "age": 30,
+    "active": true
+  },
+  {
+    "id": 2,
+    "name": "Bob",
+    "email": "bob@example.com",
+    "age": 25,
+    "active": false
+  },
+  {
+    "id": 3,
+    "name": "Charlie",
+    "email": "charlie@example.com",
+    "age": 35,
+    "active": true
+  }
+]

tests/golden/expected/json_select_mapping.txt

@@ -0,0 +1,23 @@
+[
+  {
+    "id": 1,
+    "name": "Alice",
+    "email": "alice@example.com",
+    "age": 30,
+    "active": true
+  },
+  {
+    "id": 2,
+    "name": "Bob",
+    "email": "bob@example.com",
+    "age": 25,
+    "active": false
+  },
+  {
+    "id": 3,
+    "name": "Charlie",
+    "email": "charlie@example.com",
+    "age": 35,
+    "active": true
+  }
+]

tests/golden/expected/json_to_csv.txt

@@ -0,0 +1,4 @@
+id,name,email,age,active
+1,Alice,alice@example.com,30,true
+2,Bob,bob@example.com,25,false
+3,Charlie,charlie@example.com,35,true

tests/golden/expected/json_to_json_pretty.txt

@@ -0,0 +1,23 @@
+[
+  {
+    "id": 1,
+    "name": "Alice",
+    "email": "alice@example.com",
+    "age": 30,
+    "active": true
+  },
+  {
+    "id": 2,
+    "name": "Bob",
+    "email": "bob@example.com",
+    "age": 25,
+    "active": false
+  },
+  {
+    "id": 3,
+    "name": "Charlie",
+    "email": "charlie@example.com",
+    "age": 35,
+    "active": true
+  }
+]

tests/golden/expected/json_to_yaml.txt

@@ -0,0 +1,15 @@
+- id: 1
+  name: Alice
+  email: alice@example.com
+  age: 30
+  active: true
+- id: 2
+  name: Bob
+  email: bob@example.com
+  age: 25
+  active: false
+- id: 3
+  name: Charlie
+  email: charlie@example.com
+  age: 35
+  active: true

tests/golden/expected/yaml_to_csv.txt

@@ -0,0 +1,4 @@
+id,name,email,age,active
+1,Alice,alice@example.com,30,true
+2,Bob,bob@example.com,25,false
+3,Charlie,charlie@example.com,35,true