proto: freeze the wire contract at 1.0.0

Schemas for the whole v1 surface: 38 methods, 9 events, 25 named types and the
JSON-RPC envelope, with x-privileged / x-transports / x-deadlineMs / x-errors
annotations that both generators emit as data rather than prose.

Four generators over one IR (contracts/codegen/schema_ir.py), so the C++ structs,
the TypeScript types and the OpenRPC document cannot disagree about what the
contract says:

  gen_cpp.py             -> core/generated/velox_proto.{hpp,cpp}
  gen_ts.py              -> extension/src/shared/protocol/
  gen_openrpc.py         -> contracts/openrpc.json
  gen_cpp_conformance.py -> tests/conformance/cpp/fixture_dispatcher.hpp

Inbound parsing never throws: parse<T>() returns std::expected<T, ParseError> and
nlohmann's throwing ADL from_json is deliberately not emitted. Schema constraints
(minimum, maxLength, pattern, ...) become real runtime checks in both languages —
the daemon does not trust the extension and the extension does not trust the
daemon.

59 golden fixtures: a success case per method, 12 error cases, 9 events. Replayed
by tests/conformance/ against both the generated C++ and a live server over both
transports. tools/mockd serves the same fixtures with unhappy-path flags so the
GUI and EXT lanes never wait for veloxd.

run.sh also proves capture.offer fails open: with a daemon answering slower than
750 ms the client gives up and lets Firefox take the download.

core/generated/ is libveloxproto, a separate target from libveloxcore, which
still never sees JSON — see docs/adr/0009.

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_012fgjnqFCS5h5L7gZTZo3rV

contracts/fixtures/schedule.get.json

@@ -0,0 +1,44 @@
+{
+  "name": "schedule.get \u2014 every queue's schedule",
+  "description": "queueId null asks for all of them. Backs the Scheduler window.",
+  "request": {
+    "jsonrpc": "2.0",
+    "id": 40,
+    "method": "schedule.get",
+    "params": {
+      "queueId": null
+    }
+  },
+  "response": {
+    "jsonrpc": "2.0",
+    "id": 40,
+    "result": {
+      "items": [
+        {
+          "queueId": "main",
+          "schedule": null
+        },
+        {
+          "queueId": "sync",
+          "schedule": {
+            "enabled": true,
+            "mode": "periodic",
+            "startTime": "02:00",
+            "stopTime": "06:00",
+            "daysOfWeek": [
+              1,
+              2,
+              3,
+              4,
+              5
+            ],
+            "onceDate": null
+          }
+        }
+      ]
+    }
+  },
+  "assertions": [
+    "a null schedule means the queue is under manual control"
+  ]
+}