feat(tooling): pre-ship approved library traces in optional core generator templates

Each of the five optional core package generators (events, realtime, audit,
trpc, ui) now copies pre-written decision: approved trace files into
docs/library-decisions/ at scaffold time, covering every direct runtime
dependency of that core package.

This prevents a pre-commit gate failure the first time a developer runs
pnpm turbo gen core-package <name> — the generator is the policy-compliant
path, so the traces land by construction.

- Added docs/library-decisions/*.md.hbs trace files under each of the five
  core-package template directories (15 files total)
- Updated generator config to emit traces into workspace docs/library-decisions/
  via a second emitTemplateTree call per core package
- Updated all five __snapshots__/core-package/*.snapshot.json to include the
  new trace file entries
- Added verify-doc-shas.test.ts to pin SHA256 hashes of all 15 trace templates
  so snapshot and file content cannot drift independently

ADR refs: events→ADR-015, realtime→ADR-016, audit→ADR-018;
trpc and ui cite closest ADR or null where no specific ADR exists.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

turbo/generators/config.ts

@@ -634,6 +634,11 @@ import noRealtimeHandlerReexport from "./rules/no-realtime-handler-reexport.js";
           return "Guard passed — packages/core-realtime does not exist yet.";
         },
         ...emitTemplateTree("core-package/realtime", "packages/core-realtime"),
+        ...emitTemplateTree(
+          "core-package/realtime/docs/library-decisions",
+          "docs/library-decisions",
+          { force: true },
+        ),
         ...emitTemplateTree(
           "core-package/realtime-eslint-rules",
           "packages/core-eslint/rules",
@@ -677,6 +682,11 @@ import noRealtimeHandlerReexport from "./rules/no-realtime-handler-reexport.js";
           return "Guard passed — packages/core-events does not exist yet.";
         },
         ...emitTemplateTree("core-package/events", "packages/core-events"),
+        ...emitTemplateTree(
+          "core-package/events/docs/library-decisions",
+          "docs/library-decisions",
+          { force: true },
+        ),
         () => {
           addToTranspilePackages(
             "apps/web-next/next.config.mjs",
@@ -700,6 +710,11 @@ import noRealtimeHandlerReexport from "./rules/no-realtime-handler-reexport.js";
           return "Guard passed — packages/core-trpc does not exist yet.";
         },
         ...emitTemplateTree("core-package/trpc", "packages/core-trpc"),
+        ...emitTemplateTree(
+          "core-package/trpc/docs/library-decisions",
+          "docs/library-decisions",
+          { force: true },
+        ),
         () => {
           addToTranspilePackages(
             "apps/web-next/next.config.mjs",
@@ -715,6 +730,11 @@ import noRealtimeHandlerReexport from "./rules/no-realtime-handler-reexport.js";
           return "Guard passed — packages/core-ui does not exist yet.";
         },
         ...emitTemplateTree("core-package/ui", "packages/core-ui"),
+        ...emitTemplateTree(
+          "core-package/ui/docs/library-decisions",
+          "docs/library-decisions",
+          { force: true },
+        ),
         () => {
           addToTranspilePackages(
             "apps/web-next/next.config.mjs",
@@ -730,6 +750,11 @@ import noRealtimeHandlerReexport from "./rules/no-realtime-handler-reexport.js";
           return "Guard passed — packages/core-audit does not exist yet.";
         },
         ...emitTemplateTree("core-package/audit", "packages/core-audit"),
+        ...emitTemplateTree(
+          "core-package/audit/docs/library-decisions",
+          "docs/library-decisions",
+          { force: true },
+        ),
         () => {
           addToTranspilePackages(
             "apps/web-next/next.config.mjs",