chore: sync the frontend template from 4dc033c to 8157ad4

The product was materialized from the template at `4dc033c` and has stayed
on it through 43 template commits, so it was missing all three rounds of
adapter remediation — including files it never had, such as the shared
`abortable-operation` primitive and the `exact-snapshot` decoder that
later fixes are written against. Taking only the newest round was not
possible for that reason: the delta is coherent only as a whole.

The product had not touched `src/adapters` at all since materialization,
so the 140-file delta applied with a three-way merge and no conflicts.
`package.json` was the single overlap and merged cleanly: the product owns
`name`, the template contributed `check:adapter-inventory`,
`check:remediation-ledger` and the image-resolve-signal type fixture.
All 24 product-owned files — README, index.html, CI workflow, i18n
catalog, home page, generated schemas, evidence scripts, component and
visual snapshots — are byte-identical to `main`.

`template.lock.json` now pins the synced revision and tree.

Verified in this repository, not inherited from the template: six type
projects, lint, nine gates (adapter inventory, remediation ledger,
registries, diagnostics, realtime boundaries, architecture, browser
file/storage boundaries, optional recipes, documentation), the production
build, and 2,054 of 2,073 tests. The 19 failures are all in
`tests/unit/ci-artifact-contract.test.ts` and are the same pre-existing
sandbox RLIMIT, EMFILE, umask and `/tmp` permission behaviour the template
records; four suites that failed once under parallel load pass in
isolation.

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

tests/fixtures/typecheck/invalid-image-cdn-resolve-signal.ts

@@ -0,0 +1,27 @@
+import type {
+  ImageAssetReference,
+  ImageCdnPresentationPort,
+  ImagePresetReference,
+} from "../../../src/application/ports/browser-transfer/image-cdn.ts";
+
+/**
+ * BT-IMG-01. Migration step 1.
+ *
+ * The `PRIMARY_REQUIRED` preset already reports a missing signal as
+ * `UNSUPPORTED` at runtime, which is a hidden preset precondition rather than a
+ * type-level one. This fixture pins the intended end state: `resolve()` must
+ * refuse a call with no lifetime signal at compile time.
+ *
+ * It is expected to FAIL typechecking until `signal` becomes required on the
+ * port. That flip is a separate major-contract change, per the review's own
+ * instruction not to mix it with the P1/P2 correctness work.
+ */
+declare const images: ImageCdnPresentationPort;
+declare const asset: ImageAssetReference;
+declare const preset: ImagePresetReference;
+
+// Expected error: `signal` is missing.
+void images.resolve({ asset, preset });
+
+// Expected error: `signal` may not be undefined.
+void images.resolve({ asset, preset, signal: undefined });