refactor(agents): delete dead model-selection surface and consolidate compaction targets (#122474)

* refactor(agents): delete dead model-selection surface, consolidate compaction target assembly

Removes production surface with zero live callers: buildConfiguredAllowlistKeys
(orphaned since fallback allowlist filtering was split out), the
retryTransientProviderRuntimeMiss resolveModelAsync option (its gateway startup
prewarming caller was replaced by prepared runtime snapshots), the ignored
useAsyncModelResolution plumbing (kept only as a deprecated no-op field on the
plugin-SDK-shipped prepareSimpleCompletionModelForAgent), and dead facade
re-exports (inferUniqueProviderFromCatalog, ThinkLevel, ModelRefStatus).

Consolidates resolveEmbeddedCompactionTarget's five hand-built result sites into
one assembleTarget helper owning the auth-profile-drop-on-provider-change rule;
resolution precedence is unchanged and now pinned by new table-driven cases
(unique-provider inference, ambiguous literal, profile-suffix preservation).

Net -93 production LOC, -106 test LOC.

* chore(sdk): regenerate plugin SDK API baseline after facade export removals

docs/.generated/plugin-sdk-api-baseline/tool-plugin.json

@@ -1 +1 @@
-{"contentHash":"11c6288303d0e1b2f75ad06f5acac4fbafd94ea98eaa6212d7e0adf87db43607","entrypoint":"tool-plugin","importSpecifier":"openclaw/plugin-sdk/tool-plugin"}
+{"contentHash":"f27ec37aa7c772f12aeda7b8aa969b34a7a7bb7877e6d95b26a8b3e9174f4899","entrypoint":"tool-plugin","importSpecifier":"openclaw/plugin-sdk/tool-plugin"}