Establish shared-runtime package boundaries and migration baseline - #1114

Threadplane's Angular/React runtime work needs one package ownership map and reproducible installation checks. This foundation increment keeps four private, empty scaffolds (core, content, angular, react), removes unused suffixed adapter/renderer packages and schema entry points, and assigns future rendering to framework subpaths.

• Centralizes the final nine-package dependency policy. Tests cover source, declarations, emitted artifacts and manifests, with explicit temporary exceptions for the existing Angular implementations and telemetry/browser.
• Adds the Angular APF root and checks installed local tarballs outside workspace resolution: all nine plain ESM/type exports, three isolated core exports, and the Angular root through real CLI compilation/linking with strict declaration checking.
• Checks local dependency versions/resolution, dependency isolation, parser-free framework roots, React client directives and production artifact exclusions. Angular installation measurements explicitly include compiler/build tooling.
• Routes the checks through CI and updates the capability ledger without dropping existing capabilities. Tool schema conversion and automatic argument validation are explicit omissions from the target architecture; existing populated implementations remain for their later migration.

The current Angular packages remain the supported implementation. This PR does not implement sessions, framework bindings, components, backend extraction, SSR or runtime parity. The next increment will prove one real LangGraph text/function-tool path through borrowed Angular and React bindings.

Validation on macOS arm64, Node 24.20.0 / npm 11.19.0:

• 384 focused inventory, stream, boundary, package and CI tests passed; 44 existing consumer-harness tests passed.
• All 16 scaffold lint/test/type-test/build targets passed. Empty package test targets make no runtime-coverage claim.
• Existing chat, langgraph, ag-ui, render, a2ui and telemetry lint/test/production-build targets passed; chat/langgraph/ag-ui type tests passed.
• Isolated plain consumers and the Angular CLI consumer passed. An existing Angular 21 example installed local legacy tarballs, built and passed its backend-free Chromium runtime smoke.
• Source/emitted boundaries, inventory, verification-script ESLint and whitespace checks passed. Independent specification and quality reviews were completed for each increment.

Reproduction commands and evidence are in fixtures/react-parity/. Empty-root bundle measurements are packaging evidence, not runtime performance results. Existing Angular lint/build warnings remain. Angular 20/22 and CI's Node 22 environment were not run locally. Research/planning Markdown is excluded from the commit under the contributor guide.