Generator seeds object-typed required fields with placeholder strings — 'Request property [filter] cannot be parsed'

Observation

When the positive suite is run against a live broker, 53 scenarios fail with:

```
400 Bad Request
Request property [filter] cannot be parsed
```

The generator emits e.g.:

```ts
if (ctx.filterVar === undefined) {
ctx.filterVar = seedBinding('filterVar'); // returns a plain string
}
// ...
const body1 = { filter: ctx.filterVar };
await request.post(`${baseUrl}/process-instances/cancellation`, { data: body1 });
```

But the OpenAPI schema for these batch-operation endpoints declares `filter` as an object (e.g. `{ processInstanceKey: { $eq: ... } }`), not a string. `seedBinding` falls back to a string-shaped placeholder because `seed-rules.json` has no rule matching `filterVar` / object schemas.

Reproducer

```
TEST_SEED=snapshot-baseline npm run testsuite:generate
API_BASE_URL=http://localhost:8080/v2 npx playwright test cancelProcessInstancesBatchOperation.feature.spec.ts
```

All 4 scenarios fail with the body above.

Defect class

The same root cause appears in other request-property-parse failures observed in the same run:

Two sub-classes:

1. Object-typed body fields seeded as strings (`filter`, `variables`, `changeset`). The body fails JSON binding outright.
2. String-typed but format-constrained int64 keys submitted with the literal placeholder name as a value (`processDefinitionKey: 'processDefinitionKey_8py2'`). The broker accepts the JSON but the binder rejects the cast to long.

Suggested direction

1. Extend `seed-rules.json` (or the seeding mechanism) so:
   • Properties named `filter` / `changeset` / `variables` resolve to a schema-aware empty object `{}` (or a minimal valid filter clause).
   • Properties whose JSON schema is `string` with `pattern: '^[0-9]+$'` (or `format: int64`) emit a numeric string seed like `'2251799813685000'`.
2. Alternatively: when no semantic provider is available for an int64-key consumer, fall back to omitting the optional field rather than emitting a placeholder that's guaranteed to fail the broker's binder.

Why this hides real bugs

These tests pass HTTP-layer validation but never reach the business-logic layer. A real defect in (say) batch-op filter handling would never be exercised by the current suite.

Start with seed-rules.json and the seedBinding mechanism, then run TEST_SEED=snapshot-baseline npm run testsuite:generate and the provided Playwright command against the live broker. Trace how object fields and int64-constrained string fields are seeded. Done means the affected request properties receive schema-valid values or are omitted when appropriate, and the reproduced scenarios no longer fail during request binding.