Drop private from @waybetter/runtime and @waybetter/shell (root stays
private), add per-module exports with types/import conditions backed by
a tsc build (rewriteRelativeImportExtensions rewrites .ts specifiers to
.js in dist), files/sideEffects/engines/keywords/publishConfig, a
prepublishOnly that builds and tests, and a README + copied LICENSE per
package. Root gains build:packages and pack:check scripts. dist/ is
gitignored; the desktop app keeps importing raw src/*.ts by relative
path, unaffected.
