Most of SemanticRouter.AspNetCore's 185 public top-level types are implementation details; trim the surface to the documented extension points before 1.0 #200

What

SemanticRouter.AspNetCore exposes 213 public types and 1562 members. The documented extension surface is much smaller:

• README.md "Extensibility" (README.md:598-610) and docs/architecture.md:133-150 name about 20 interfaces, including IChatConnector, IChatConnectorFactory, IModelDiscovery, IRouterConfigurationStore, IEmbeddingProviderFactory, IToolCallAffinity, IWarmCacheStore, IRoutingActivityStore, IRouterConfigurationHistory, IUsageLedger, IPromptExtractor and IRouterSecretStore.
• Add SemanticRouterBuilder, the Use* / Map* / Add* extensions and the options types.

Of the 185 top-level public types, 145 are never named in docs/, README.md or samples/. Many are helpers that only first-party code calls, and every one of those first-party callers already has InternalsVisibleTo.

Used by nothing outside AspNetCore except tests:

• ActivityReports, LocalOnlySignals, RoutingFeedbackLog, MemoryExposureLog
• ModelFamily, ModelFamilyBand, ModelFamilyFile
• InMemoryEvaluationSetStore, JsonLinesEvaluationSetStore, ProtectedFileSecretStore, OpenAICompatibleEmbeddingProvider
• ClaudeCodeMemorySource, KnowledgeGraphMemorySource, MarkdownMemorySource
• ClientTurnFile, DashboardTheme, ThemeContrastIssue, SecretRedactor

Used only by SemanticRouter.Hosting, which has InternalsVisibleTo (SemanticRouter.AspNetCore.csproj:39):

• RouterDoctor, RouterCheck, RouterCheckStatus
• ModelLineup, ModelLineupEntry, ModelLineupReport
• ConnectorProbe, ConnectorProbeResult, ConnectorProbeFailure
• SecretReference, ModelFamilyTable

Used by Hosting and Desktop: MachinePolicyLoader, MachinePolicy.

Used by the sibling packages through InternalsVisibleTo:

• Storage.Sqlite: UsageSummaries, WarmCacheStore, ToolCallAffinity, InMemoryAuditLog, InMemoryUsageLedger, InMemoryTuningStore, InMemoryRouterConfigurationHistory
• Copilot: CliExecutableLocator, CliExecutableLookup

The concrete RoutingActivityLog and the mutable RoutingActivityEntry (29 public setters) are public too. That class is shared across request threads and handed to IRoutingActivityStore, so its shape becomes a contract.

Evidence

• A generated type list for the package, with each type's usage checked by grep -rlw <Type> src docs README.md samples tests.
• The extension tables in the docs: README.md:598-610, docs/architecture.md:133-150.

Impact

At 1.0, every one of these types and members becomes a semver commitment. Refactoring the doctor, the model-family table, the memory sources or the dashboard theme loader would then need a major version. The noise also hides the real extension points, which makes the API harder to learn.

Suggested fix

Do one deliberate API review pass before 1.0:

• For each public type, decide:
  • a documented extension point or option: it stays public, or
  • an implementation detail: it becomes internal.
• Hosting and Tests already have InternalsVisibleTo. Desktop would need it for MachinePolicyLoader, or the loader moves to Hosting.
• Do not add new InternalsVisibleTo for the shipped siblings (see the sibling-package sub-issue). If Sqlite or Copilot need a type, it is public API and gets documented.
• Record the outcome in PublicAPI.Shipped.txt (see the package-validation sub-issue), so that later additions are visible in review.

Done when

• Every public type in SemanticRouter.AspNetCore is named in the extensibility and API docs, or is an options or result type of an API that is.
• The helper and static utility classes listed above are internal, or documented with a reason to stay public.
• The 1.0 release notes record the public type count, and package validation locks the API.