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/lib/core-package-utils.ts

@@ -1,4 +1,10 @@
-import { existsSync, readFileSync, writeFileSync, readdirSync, statSync } from "node:fs";
+import {
+  existsSync,
+  readFileSync,
+  writeFileSync,
+  readdirSync,
+  statSync,
+} from "node:fs";
 import { join, relative } from "node:path";
 import type { PlopTypes } from "@turbo/gen";
 
@@ -61,8 +67,7 @@ export function splicePluginRulesAt(
   }
   const after = source.slice(idx + anchor.length);
   if (after.trimStart().startsWith(block.trim())) return; // idempotent
-  const updated =
-    source.slice(0, idx + anchor.length) + "\n" + block + after;
+  const updated = source.slice(0, idx + anchor.length) + "\n" + block + after;
   writeFileSync(filePath, updated);
 }
 
@@ -97,7 +102,10 @@ export function addBoundariesEntry(
   }
   const modeFragment = opts.mode ? `, mode: "${opts.mode}"` : "";
   const newEntry = `        { type: "core", pattern: "${packagePath}"${modeFragment} },\n`;
-  const updated = source.replace(wildcardLine[0], `\n${newEntry}${wildcardLine[1]}`);
+  const updated = source.replace(
+    wildcardLine[0],
+    `\n${newEntry}${wildcardLine[1]}`,
+  );
   writeFileSync(baseJsPath, updated);
 }
 
@@ -106,11 +114,13 @@ export function addBoundariesEntry(
  * file, returns a plop `add` action that emits the file (without .hbs
  * extension) at <destPrefix>/<relative-path>. The actions are sorted so
  * directory creation is deterministic.
+ *
+ * Set `opts.force` to overwrite existing files (idempotent re-runs).
  */
 export function emitTemplateTree(
   srcPrefix: string,
   destPrefix: string,
-  opts: { templatesRoot?: string } = {},
+  opts: { templatesRoot?: string; force?: boolean } = {},
 ): PlopTypes.AddActionConfig[] {
   // The templates directory is resolved in priority order:
   // 1. opts.templatesRoot — test injection (temp directory)
@@ -120,13 +130,18 @@ export function emitTemplateTree(
   if (opts.templatesRoot) {
     root = opts.templatesRoot;
   } else {
-    const fromRepoRoot = join(process.cwd(), "turbo", "generators", "templates");
+    const fromRepoRoot = join(
+      process.cwd(),
+      "turbo",
+      "generators",
+      "templates",
+    );
     const fromGeneratorsDir = join(process.cwd(), "templates");
     root = existsSync(fromRepoRoot) ? fromRepoRoot : fromGeneratorsDir;
   }
   const srcRoot = join(root, srcPrefix);
   const out: PlopTypes.AddActionConfig[] = [];
-  walkHbs(srcRoot, srcRoot, srcPrefix, destPrefix, out);
+  walkHbs(srcRoot, srcRoot, srcPrefix, destPrefix, out, opts.force ?? false);
   out.sort((a, b) => (a.path ?? "").localeCompare(b.path ?? ""));
   return out;
 }
@@ -137,11 +152,12 @@ function walkHbs(
   srcPrefix: string,
   destPrefix: string,
   out: PlopTypes.AddActionConfig[],
+  force: boolean,
 ): void {
   for (const name of readdirSync(dir)) {
     const full = join(dir, name);
     if (statSync(full).isDirectory()) {
-      walkHbs(topRoot, full, srcPrefix, destPrefix, out);
+      walkHbs(topRoot, full, srcPrefix, destPrefix, out, force);
       continue;
     }
     if (!name.endsWith(".hbs")) continue;
@@ -149,8 +165,12 @@ function walkHbs(
     out.push({
       type: "add",
       path: join(destPrefix, rel).replace(/\\/g, "/"),
-      templateFile: join("templates", srcPrefix, relative(topRoot, full)).replace(/\\/g, "/"),
+      templateFile: join(
+        "templates",
+        srcPrefix,
+        relative(topRoot, full),
+      ).replace(/\\/g, "/"),
+      force,
     } as PlopTypes.AddActionConfig);
   }
 }
-