refactor: retire August compat windows (embedding API, pi aliases, target parser, spawning hook, setup exports, WhatsApp inbound aliases) (#124416)

* refactor(plugin-sdk): retire embedded Pi aliases

* refactor(channels): retire explicit target compatibility

* refactor(plugins): retire subagent spawning hook

* refactor(plugin-sdk): retire shipped channel setup exports

* refactor(whatsapp): retire inbound callback aliases

Proof: focused build and WhatsApp E2E green; broad WhatsApp suite 188/189 files green. extensions/whatsapp/src/monitor-inbox.policy.test.ts flakes only in the parallel batch and passes isolated (10/10).

* refactor(plugin-sdk): retire memory embedding registrar

Migrate every bundled provider and manifest to registerEmbeddingProvider and contracts.embeddingProviders. Preserve memory-specific batching, local-service acquisition, index identity, and auto-selection through the canonical generic registry adapter, then remove the parallel registrar, registry, diagnostics, contracts, tests, and docs.

* chore(plugin-sdk): tighten retired surface budgets

Pin the post-retirement public SDK surface to 144 entrypoints, 4,312 exports, 2,564 callable exports, and 1,133 deprecated exports; agent-harness-runtime now permits exactly nine deprecated exports.

docs/plugins/reference/github-copilot.md

@@ -16,7 +16,7 @@ Adds GitHub Copilot model provider support to OpenClaw.
 
 ## Surface
 
-providers: `github-copilot`; contracts: `memoryEmbeddingProviders`, `usageProviders`
+providers: `github-copilot`; contracts: `embeddingProviders`, `usageProviders`
 
 ## Related docs