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/schema/methods/session.pair.schema.json

@@ -0,0 +1,32 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://velox.dev/schema/methods/session.pair.schema.json",
+  "title": "session.pair",
+  "description": "WebSocket transport only. Triggers a GUI or desktop-notification prompt showing a four-digit code; the user must approve before a token is issued. Failed attempts are rate-limited to 5/min followed by a 60 s lockout (-32014) so a token cannot be brute-forced by another local process. The daemon stores only a hash of the token.",
+  "x-privileged": false,
+  "x-transports": ["ws"],
+  "x-deadlineMs": 120000,
+  "x-errors": [-32003, -32014],
+  "type": "object",
+  "properties": {
+    "params": {
+      "type": "object",
+      "additionalProperties": false,
+      "required": ["clientName", "extensionId"],
+      "properties": {
+        "clientName":  { "type": "string", "maxLength": 64 },
+        "extensionId": { "type": "string", "description": "The moz-extension origin UUID. Must match the Origin header verified on the WS upgrade." },
+        "code":        { "type": ["string", "null"], "pattern": "^[0-9]{4}$", "description": "Set when the user typed the code into the extension's Options page instead of clicking Allow in the GUI." }
+      }
+    },
+    "result": {
+      "type": "object",
+      "additionalProperties": false,
+      "required": ["token", "expiresAt"],
+      "properties": {
+        "token":     { "type": "string", "minLength": 43, "description": "256 bits, base64url. Stored by the extension in browser.storage.local and sent on every later connect." },
+        "expiresAt": { "type": ["string", "null"], "format": "date-time", "description": "null means the token does not expire; it is revoked from Options -> Unpair." }
+      }
+    }
+  }
+}