chore: sync the frontend template from a0fbafb to 5434760

Carries eight template commits: the provider sandbox actually running, release
admission to a named environment, the product feature manifest with its runtime
kill switch, architecture and documentation rules that match what is enforced,
the removability fixtures, and the browser, visual and performance evidence.

Product identity is unchanged. `package.json` keeps `tech-log-frontend` and the
catalog keeps the Tech Log naming; the home page was not in the delta. The
visual baselines are this product's own — the template's were excluded from the
transplant and these were regenerated here, where the only difference is the
platform overview's new product-feature section.

What this repository gains operationally: `config/runtime/{local,development,
staging,production}.json` with `FE-GATE-027` refusing an artifact whose runtime
document does not match the environment it is being admitted to, and
`FEATURE_OVERRIDES` for taking an installed feature out of service without a
rebuild.

Verified here: eight gates green, build green, visual 5/5, and 1,858 of 1,859
tests in the suites that do not need a sandbox — the one failure passes in
isolation and is a jsdom lazy-chunk timeout under parallel load. The provider
suites cannot run on this machine at all: `kernel.apparmor_restrict_unprivileged
_userns=1` makes `bwrap --unshare-net` fail, reproducible without any code from
either repository.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

scripts/lib/promotion-stager.ts

@@ -6,7 +6,6 @@ import {
 import { constants } from "node:fs";
 import {
   lstat,
-  mkdir,
   open,
   readdir,
   rm,
@@ -38,6 +37,7 @@ import {
 } from "./ci-candidate-archive.ts";
 import { verifyArchivedLocalEvidence } from "./local-release-evidence.ts";
 import { readBoundedRegularFile } from "./ci-artifact-validator.ts";
+import { makePrivateDirectory } from "./private-filesystem.ts";
 
 
 export type StagedFile = Readonly<{
@@ -334,6 +334,18 @@ export async function cleanupFinalizedPromotion(input: Readonly<{
       await dependencies.beforeRemove?.();
       const visibleParent = await lstat(parent);
       assertRunnerTempIdentity(visibleParent, input.runnerTempIdentity);
+      // Re-bind the name to the inode before removing anything.
+      //
+      // The removals below run through the pinned staging descriptor, so they
+      // always reach the owned inode even after the name has been re-pointed
+      // somewhere else. That is safe for the substitute, but it destroys this
+      // promotion's exact five first and only reports the substitution
+      // afterwards — a caller that retries then finds a half-emptied staging
+      // directory and no way to tell a completed cleanup from an interrupted
+      // one. Detecting the swap here makes the failure total: nothing is
+      // removed unless the leaf still is what was validated.
+      assertStagingIdentity(await lstat(descriptorExpected), input.stagingIdentity);
+      assertStagingIdentity(await stat(stagingDescriptorRoot), input.stagingIdentity);
       for (const name of PROMOTED_FILE_NAMES) {
         await rm(path.join(stagingDescriptorRoot, name), { force: false });
       }
@@ -456,7 +468,7 @@ export async function publishPrivatePromotionStaging(
   try {
     const procMetadata = await stat(descriptorRoot);
     if (!procMetadata.isDirectory()) throw new Error("descriptor-relative staging is unavailable");
-    await mkdir(descriptorStaging, { mode: 0o700 });
+    makePrivateDirectory(descriptorStaging);
     ownsStaging = true;
     const createdStaging = await lstat(descriptorStaging);
     if (!createdStaging.isDirectory() || createdStaging.isSymbolicLink()) {