feat: add actions to FeedSource interface

Add listActions() and executeAction() to FeedSource for write
operations back to external services. Actions use arktype schemas
for input validation via StandardSchemaV1.

- ActionDefinition type with optional input schema
- FeedEngine routes actions with existence and ID validation
- Source IDs use reverse-domain format (aris.location, aris.tfl)
- LocationSource: update-location action with schema validation
- TflSource: set-lines-of-interest action with lineId validation
- No-op implementations for sources without actions

Co-authored-by: Ona <no-reply@ona.com>

bun.lock

@@ -35,6 +35,9 @@
     "packages/aris-core": {
       "name": "@aris/core",
       "version": "0.0.0",
+      "dependencies": {
+        "@standard-schema/spec": "^1.1.0",
+      },
     },
     "packages/aris-data-source-weatherkit": {
       "name": "@aris/data-source-weatherkit",
@@ -66,6 +69,7 @@
       "version": "0.0.0",
       "dependencies": {
         "@aris/core": "workspace:*",
+        "arktype": "^2.1.0",
       },
     },
     "packages/aris-source-tfl": {