refactor: le paquet s'appelle polyfill, « SDK » désigne celui de NextGraph

Le nom @ng-eventually/sdk entrait en collision avec le SDK de NextGraph, dont
ce paquet est justement un polyfill. Impossible d'écrire « le SDK » sans lever
l'ambiguïté à chaque phrase — et le contrat publié, lu par une application,
était le pire endroit pour laisser traîner ça.

packages/sdk → packages/polyfill, @ng-eventually/sdk → @ng-eventually/polyfill,
contract_sdk-surface → contract_polyfill-surface, e2e/sdk-entry.ts →
e2e/polyfill-entry.ts, docs/sdk-reference.md → docs/polyfill-reference.md.

Les occurrences de « SDK » qui désignent celui de NextGraph restent intactes,
y compris les chemins dans nextgraph-rs (sdk/js/orm, sdk/js/web). Le tri s'est
fait occurrence par occurrence, pas par substitution.

Le contrat énonce désormais son identité en une phrase : « This package is a
polyfill of NextGraph's SDK. »

examples/notebook/README.md

@@ -1,12 +1,12 @@
 # Notebook — the library's example application
 
-A minimal application written against `@ng-eventually/sdk`, in plain DOM.
+A minimal application written against `@ng-eventually/polyfill`, in plain DOM.
 
 It exists for two reasons, and the second is the one that matters.
 
-**It shows how to use the library.** Every call in `app.ts` is what a real consumer writes. There is no test scaffolding, no privileged import, no reaching into the library's internals — it resolves `@ng-eventually/sdk` as an external consumer does. If something reads awkwardly here, it reads awkwardly for everyone.
+**It shows how to use the library.** Every call in `app.ts` is what a real consumer writes. There is no test scaffolding, no privileged import, no reaching into the library's internals — it resolves `@ng-eventually/polyfill` as an external consumer does. If something reads awkwardly here, it reads awkwardly for everyone.
 
-**It is what the applicative e2e suite drives** (`packages/sdk/e2e/notebook.ts`, `bun run test:e2e:app`). The other suite talks to a bag of methods on `window.__sdk`, which proves the functions run but never that an application can be written with them — and that gap shipped a real defect once: a document's inbox was green in tests and unusable in practice, because the harness handed an address across an identity boundary through a variable, something no application can do. Here each identity is its own browser page, and the only values that cross between them are the ones that cross in life: a note's reference, copied off one screen, and an identifier typed into a field.
+**It is what the applicative e2e suite drives** (`packages/polyfill/e2e/notebook.ts`, `bun run test:e2e:app`). The other suite talks to a bag of methods on `window.__sdk`, which proves the functions run but never that an application can be written with them — and that gap shipped a real defect once: a document's inbox was green in tests and unusable in practice, because the harness handed an address across an identity boundary through a variable, something no application can do. Here each identity is its own browser page, and the only values that cross between them are the ones that cross in life: a note's reference, copied off one screen, and an identifier typed into a field.
 
 It has already paid for itself: writing it surfaced that `UnionSubject` returned `string` where the values are always document references (so a consumer had to cast whatever it had just read before passing it back), and that the access gate normalized what a user typed but not what the URL carried.
 
@@ -27,4 +27,4 @@ It has also found three defects of its own, each one the harness could not see.
 
 ## Running it
 
-`cd packages/sdk && bun run test:e2e:app` builds it, serves it, and drives it against the real broker. To open it by hand you need a wallet: serve the folder with a bundled `app.js` and a `/shared-wallet.ngw`, and set `__NOTEBOOK_WALLET_PASSWORD__`.
+`cd packages/polyfill && bun run test:e2e:app` builds it, serves it, and drives it against the real broker. To open it by hand you need a wallet: serve the folder with a bundled `app.js` and a `/shared-wallet.ngw`, and set `__NOTEBOOK_WALLET_PASSWORD__`.

examples/notebook/app.ts

@@ -1,5 +1,5 @@
 /**
- * Notebook — a minimal application written against `@ng-eventually/sdk`.
+ * Notebook — a minimal application written against `@ng-eventually/polyfill`.
  *
  * It exists for two reasons, and the second is the one that matters:
  *
@@ -7,7 +7,7 @@
  *    writes; there is no test scaffolding, no privileged import, no reaching into the
  *    library's internals. If something is awkward here, it is awkward for everyone.
  *
- * 2. **It is what the applicative e2e suite drives** (`packages/sdk/e2e/notebook.ts`).
+ * 2. **It is what the applicative e2e suite drives** (`packages/polyfill/e2e/notebook.ts`).
  *    The other suite talks to a bag of methods on `window.__sdk`, which proves the
  *    functions run but never that an application could be written with them — and that
  *    gap shipped a real defect: a document's inbox was green in tests and unusable in
@@ -40,7 +40,7 @@ import {
   type Scope,
   // Polyfill-era — ONE call, and it is the whole of what goes away.
   configure,
-} from "@ng-eventually/sdk";
+} from "@ng-eventually/polyfill";
 import { ng as realNg, init as realInit } from "@ng-org/web";
 
 // --- the domain, such as it is ---------------------------------------------

examples/notebook/package.json

@@ -2,9 +2,9 @@
   "name": "@ng-eventually/example-notebook",
   "private": true,
   "type": "module",
-  "description": "A minimal application written against @ng-eventually/sdk \u2014 the library's usage example, and what the e2e suite drives.",
+  "description": "A minimal application written against @ng-eventually/polyfill \u2014 the library's usage example, and what the e2e suite drives.",
   "dependencies": {
-    "@ng-eventually/sdk": "workspace:*",
+    "@ng-eventually/polyfill": "workspace:*",
     "@ng-org/web": "0.1.2-alpha.13"
   }
 }

examples/notebook/tsconfig.json

@@ -10,8 +10,8 @@
       "DOM"
     ],
     "paths": {
-      "@ng-eventually/sdk": [
-        "../../packages/sdk/src/index.ts"
+      "@ng-eventually/polyfill": [
+        "../../packages/polyfill/src/index.ts"
       ]
     }
   },