feat(collaborative-vue): optional collaborate() proxy for v-model (stacked on #1041)

[mmamedel]

Important

Stacked on #1041 (the collaborative-vue composables). This branch contains #1041's commit as a dependency, so the diff currently shows both. Please review/merge #1041 first; the only new commit here is ed998ec (the optional collaborate() proxy). Once #1041 lands, this reduces to just that commit.

What

Adds an optional high-level collaborate(model) to @jsonjoy.com/collaborative-vue — a single fine-grained reactive state proxy you read and mutate like a plain object, purpose-built for Vue v-model two-way binding, which the low-level composables (#1041) serve awkwardly.

<script setup lang="ts">
import {Model} from 'json-joy/lib/json-crdt';
import {collaborate} from '@jsonjoy.com/collaborative-vue';

const {state} = collaborate<Board>(Model.create({title: 'Untitled', notes: []}));
</script>

<template>
  <input v-model="state.title" />        <!-- two-way bound to the CRDT -->
  <li v-for="(n, i) in state.notes" :key="i"><input v-model="n.text" /></li>
</template>

Why a separate, additive layer

This keeps the project's layering — node API ← composables ← optional sugar — rather than competing with it:

• It is sugar over the composables: reactivity uses the same per-node onNodeChange('self') subscription; writes dispatch through json-joy's existing node verbs (ObjApi.set/del, ArrApi.ins/upd/del/merge, VecApi.set).
• No additions to json-joy core (this is the rewrite of the originally-proposed .w API, now living entirely in the binding).
• Reads subscribe per node, so a remote applyPatch re-renders only the nodes that changed — no reconcile pass, no echo guard, no second store.
• For precise control (in-place text ops, merge vs set, explicit self/child/subtree granularity) you drop down to the composables; the proxy doesn't hide them.

API

• collaborate<T>(model): { state: T; dispose(): void }
• dispose() runs automatically when called inside a component setup() (via onScopeDispose).

Tests

5 tests (jest + watchEffect), all green: reads mirror the view; plain assignment + array methods record ops; fine-grained (a title edit doesn't re-run an effect reading the notes); remote-patch convergence re-renders the affected node; dispose() stops reacting. Builds via the root solution tsc -b.