…ved ObjectStackCapabilities schema (#4781)

`content/docs/protocol/kernel/runtime-capabilities.mdx` documented
`ObjectStackCapabilities` (data/ui/system subsystem descriptors) end to end,
including two full `const capabilities: ObjectStackCapabilities = {...}`
examples and a `hasCapability()` helper. That schema was removed in #3605:
`import type { ObjectStackCapabilities } from '@objectstack/spec'` is TS2305,
and none of the tabled keys (`queryDistinct`, `queryHaving`, `queryJoins`,
`geoSpatial`, …) exist in any live schema. The page named "AI Agents:
Understanding platform constraints for code generation" as an audience, so it
was teaching a non-existent capability-negotiation surface to code generators.

Delete the page. The live mechanisms are the REST discovery endpoint and the
driver-side `DriverCapabilities` (post-#4634).

The page's trailing "Discovery Endpoint" section was NOT accurate either and is
deliberately not moved verbatim. Checked against the implementation:

  - `ObjectStackProtocolImplementation.getDiscovery()`
    (packages/metadata-protocol/src/protocol.ts) returns
    `{ version, apiName, routes, services, capabilities }` — no `name`, no
    `environment`, no `locale`. The page showed all three on
    `GET /api/v1/discovery`; those fields belong to the *dispatcher*-served
    `/.well-known/objectstack` payload (packages/runtime/src/http-dispatcher.ts
    `getDiscoveryInfo`), which `content/docs/api/index.mdx` already documents
    correctly and separately.
  - The page's sample carried `routes.graphql: "/graphql"`. `ApiRoutesSchema`
    (packages/spec/src/api/discovery.zod.ts) has no `graphql` key and
    `serviceToRouteKey` never maps one — flatly wrong.
  - `version: "1.0.0"` — the REST handler overrides it with
    `config.api.version` (`v1`).

Folded into content/docs/api/index.mdx only the parts that verify:

  - `GET /api/v1` and `GET /api/v1/discovery` are one handler registered at two
    paths (`registerDiscoveryEndpoints`, packages/rest/src/rest-server.ts), and
    the dispatcher cedes `<basePath>/discovery` to REST when mounted
    (ADR-0076 D11) — it owns the route only in REST-less compositions.
  - The `capabilities` map and `transactionalBatch` (#3298 / ADR-0034): true
    iff `POST {basePath}/batch` is mounted AND the engine can honour a
    transaction (protocol derives it from `engine.transaction`, rest-server
    ANDs it with `api.enableBatch`).

Also: meta.json nav entry removed; the two inbound links (automation/index.mdx,
kernel/index.mdx) repointed; scripts/role-word-baseline.json ratcheted down for
the removed file (check-role-word fails on a vanished baselined file).

Docs-only, releases nothing — empty changeset.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018iARDqtrhQgz6fVHDeDkbQ