docs: rename migration notes to v2-to-v3

Author: aleclarson

README.md

@@ -139,7 +139,7 @@ for await (const event of await client.events()) {
 
 ## Documentation
 
-- [Concepts, API selection, and v2.0.1 migration notes](docs/context.md)
+- [Concepts, API selection, and v2->v3 migration notes](docs/context.md)
 - [Runnable shared-route example](examples/basic-usage.ts)
 - [Runnable NDJSON response-stream example](examples/ndjson-stream.ts)
 - Generated declarations in the published package provide the exact signatures

docs/context.md

@@ -329,10 +329,10 @@ the thrown `Error`.
 response helper as-is; Rouzer does not automatically parse a returned `Response`
 from `onJsonError`.
 
-### Update code written for v2.0.1
+### v2->v3 migration
 
 Rouzer now uses action/resource route trees for router registration and client
-shorthands. A v2.0.1 method-map route such as this:
+shorthands. In the v2->v3 migration, a method-map route such as this:
 
 ```ts
 export const profileRoute = route('profiles/:id', {