feat(go-config): multi-format codecs, envc CLI, fixtures, ASRs

- Module github.com/eslider/go-config with env/yaml/json/ini packages
- internal: source, keymap, merge, structconv, bytesutil
- cmd/envc: convert, get, merge
- docs/asr ASR-0001..0008, README/CHANGELOG/AGENTS refresh
- golangci-lint v2 config; tests + fixtures

Co-authored-by: Cursor <cursoragent@cursor.com>

fixtures/identity/service.env

@@ -0,0 +1,7 @@
+SERVICE_NAME=my-service
+SERVICE_SUBSERVICE_NAME=abc
+SERVICE_SUBSERVICE_KEY=abs
+SERVICE_SUBSERVICE_TIMEOUT=30
+SERVICE_SUBSERVICE_ENABLED=true
+SERVICE_DATABASE_URL=postgres://localhost:5432/db
+SERVICE_DATABASE_POOLSIZE=10

fixtures/identity/service.ini

@@ -0,0 +1,12 @@
+[service]
+name = my-service
+
+[service.subservice]
+name = abc
+key = abs
+timeout = 30
+enabled = true
+
+[service.database]
+url = postgres://localhost:5432/db
+pool-size = 10

fixtures/identity/service.json

@@ -0,0 +1,15 @@
+{
+  "service": {
+    "name": "my-service",
+    "sub-service": {
+      "name": "abc",
+      "key": "abs",
+      "timeout": 30,
+      "enabled": true
+    },
+    "database": {
+      "url": "postgres://localhost:5432/db",
+      "pool-size": 10
+    }
+  }
+}

fixtures/identity/service.yaml

@@ -0,0 +1,10 @@
+service:
+  name: my-service
+  sub-service:
+    name: abc
+    key: abs
+    timeout: 30
+    enabled: true
+  database:
+    url: postgres://localhost:5432/db
+    pool-size: 10