Export the dev-runtime provider protocol types (start context, session, inspection envelope, generation store, MCP registry) from agent-bundle/api

[ScriptedAlchemy]

Problem

dev.runtime.provider is a documented configuration key (website/docs/en/reference/configuration.mdx:153) and agent-bundle/api exports the provider entry type — DevRuntimeProvider, CreateDevRuntimeProvider, AgentBundleDevRuntimeConfig (packages/agent-bundle/src/api.ts:245-249). But a provider cannot be written against that export alone: every type the start() contract hands in or expects back — the start context, the session, the inspection envelope, the MCP server descriptor, the generation store and MCP registry a session must drive — lives only in packages/agent-bundle/src/dev/**. The one example that implements a provider therefore reaches into the package source with ../../../../packages/agent-bundle/src/dev/* imports, which contradicts the "public exports only" rule for examples/* and means no out-of-tree consumer can implement dev.runtime.provider with types at all.

This is distinct from #459 (what a context provider receives at request time); this issue is about the dev-runtime provider protocol behind dev.runtime.provider.

Evidence

All import sites are in examples/rsc-agent-runtime on main (after #473 moved JsonObject/JsonValue to the root export and DevRuntimeProvider to agent-bundle/api; the rest have no public home):

Source module	Names reached only through packages/agent-bundle/src/dev/**	Import sites
dev/runtime-provider.ts	DevRuntimeStartContext, DevRuntimeSession, DevRuntimePreparedProject, DevRuntimeEventInput, DevRuntimeClientSurfaceEndpoint, DevRuntimeMcpSession, DevRuntimeMcpSessionCloseObservation, DevRuntimeUnavailableError, DevRuntimeGenerationConflictError	src/dev/rsbuild-runtime-session.ts:57-67, src/dev/generation-materializer.ts:19, tests/generation-materializer.test.ts:31; src/dev/provider.ts now derives DevRuntimeStartContext as Parameters<DevRuntimeProvider['start']>[0] to avoid the deep import
dev/runtime-protocol.ts	DevRuntimeAsset, DevRuntimeAssetRequest, DevRuntimeDescriptor, DevRuntimeDiagnostic, DevRuntimeFixture, DevRuntimeInspectionEnvelope, DevRuntimeInvocationRequest, DevRuntimeMcpConnectionState, DevRuntimeMcpRegistryReconcileInput, DevRuntimeMcpServerDescriptor, DevRuntimeMcpSessionBinding, DevRuntimeReplayRequest, DevRuntimeRun, DevRuntimeStateIdentity, DevRuntimeStateResetRequest, DevRuntimeStatus, DevRuntimeSurface, DevRuntimeTraceSpan, DevRuntimeTreeNode, RuntimeVector	src/dev/rsbuild-runtime-session.ts:68-86, src/dev/serialize-inspection.ts:3-7, src/runtime/contracts.ts:2-5, src/dev/generation-materializer.ts:20
dev/runtime-generation-store.ts	RuntimeGenerationStore (class), RuntimeGeneration, RuntimeGenerationActivationGuard, RuntimeGenerationAsset, RuntimeGenerationCandidate, RuntimeGenerationManifestInput, RuntimeGenerationMetadataCodec, RuntimeGenerationPreparedActivation, RuntimeGenerationValidationInput	src/dev/rsbuild-runtime-session.ts:43-49, src/dev/generation-materializer.ts:22-31, tests/generation-materializer.test.ts:30, tests/environment-checkpoint-store.test.ts:21
dev/runtime-mcp-registry.ts	RuntimeMcpRegistry (class), RuntimeMcpConnection, RuntimeMcpConnector, RuntimeMcpExecutionContext, RuntimeMcpPreparedActivationReconcile	src/dev/rsbuild-runtime-session.ts:50-56
dev/index.ts, dev/epoch-store.ts, dev/runtime-provider-loader.ts, core/digest.ts (test-only)	ProjectService, ArtifactService, EpochStore, resolveDevRuntimeProvider, digest, stableJson	tests/dev-provider.integration.test.ts:8-13, tests/dev-invocation.integration.test.ts:14, tests/generation-materializer.test.ts:29

The example's README already labels itself "an architecture experiment, not an agent-bundle public API", so it does not block anything today; it does mean the dev.runtime.provider key is documented without a typed way to satisfy it.

Proposed shape

Export the provider protocol from agent-bundle/api, next to DevRuntimeProvider:

1. Types the DevRuntimeProvider contract references transitively (everything a provider must accept or return): the runtime-provider.ts and runtime-protocol.ts rows above, as export type. These are already the wire/session protocol the Workbench consumes, so exporting them is a naming decision, not a new surface.
2. The two error classes DevRuntimeUnavailableError and DevRuntimeGenerationConflictError as values — a provider has to throw them to get the documented Workbench behaviour.
3. RuntimeGenerationStore and RuntimeMcpRegistry as values plus their option/candidate types. If keeping the classes internal is preferred, DevRuntimeStartContext should instead hand a provider pre-constructed store/registry instances so a provider never needs to import them.
4. Leave ProjectService, ArtifactService, EpochStore, resolveDevRuntimeProvider, digest, stableJson internal; they are reached only from the example's tests, which can move to the agent-bundle/test dev-epoch level (runDevEpochContractMatrix) or stay deep-import as test-only wiring.

TypeDoc compiles packages/agent-bundle/src directly, so the api reference page follows automatically; the pnpm docs:site:build gate applies.

Acceptance

• import type { DevRuntimeStartContext, DevRuntimeSession, DevRuntimeInspectionEnvelope, DevRuntimeMcpServerDescriptor, /* … */ } from 'agent-bundle/api' resolves, and import { DevRuntimeUnavailableError, DevRuntimeGenerationConflictError } from 'agent-bundle/api' resolves.
• examples/rsc-agent-runtime/src/** contains no packages/agent-bundle/src path import (rg "packages/agent-bundle/src" examples/rsc-agent-runtime/src is empty); the four src/dev/*.ts and src/runtime/contracts.ts files import from agent-bundle/api instead.
• The public-API declaration test (packages/agent-bundle/tests/public-api.test.ts / public-api-packed.test.ts) covers the new names, and website/docs/{en,zh}/reference/configuration.mdx dev.runtime.provider links to the agent-bundle/api types a provider implements.
• A changeset (patch) names the new agent-bundle/api exports.

Found while auditing the examples against the public surface in #473.