chore(maintenance): make the root tsconfig an options base with no program

[svozza]

Summary

The root tsconfig.json carried a references array that had drifted to eleven of fifteen packages. The root is only an options base: every project extends it and lists its own files, and TypeDoc in packages mode reads compilerOptions from it while taking file lists from each package's own tsconfig. The array existed solely to keep the root loadable, since TypeScript rejects a bare files: [] with no include or references. This PR replaces the list with the minimal shape TypeScript and TypeDoc accept for a config with no inputs, so there is nothing left to drift.

Changes

• tsconfig.json: drop references; keep files: [] and add empty include and references arrays with a comment explaining why both are needed. The root compiles nothing, so a bare tsc at the root stays a no-op.
• tsconfig.cjs.json: add files: [] so the CommonJS base stays valid on its own now that it no longer inherits the list.
• CODING_STANDARDS.md: the verification section pointed at npm run tsc, which no workspace defines. Since every tests/tsconfig.json includes ../src, the build:tests bullet now states it type-checks source and tests, and notes npm run build also compiles the CommonJS target.

Verified with the real docs build, mkdocs build on Python 3.12 as CI uses it: exit 0, TypeDoc runs through the mkdocs-typedoc plugin without a config error, and site/api has the same 134 module pages as before. Also tsc -p on both root configs is valid and compiles nothing; a package build, a package build:tests and the snippets type-check all pass. Removing the list without the empty arrays fails TypeDoc with TS18002 and would have published an empty API Reference, since the docs build runs mkdocs in non-strict mode.

Issue number: closes #5644

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