fix(client-web): reject unknown web kind, lock fixture to contract, observe web card in boot smoke

- webCardModel returns null for an unknown web `kind` (wire from a newer host)
  instead of drawing it as a malformed fetch, matching the unknown-`card` and
  terminal-model wire-boundary default.
- Fixture WEB_SEARCH_RESULT/WEB_FETCH_RESULT and the source type derive from the
  contract's ToolResultView via Extract, so a new contract field fails at the
  type level rather than drifting silently.
- built-boot smoke asserts the web_search/web_fetch turns render their keyed
  WebRow cards, giving the registration and wire projection an assembled check.
- DetailsPanel comment no longer claims the card omits content for search.
- ui-primitives README inline-Chinese limitation now lists WebBlock's controls.

packages/client/ui-primitives/README.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write packages/client/ui-primitives/README.md
-README.md: b5b79f7f0d01afb2d06fb18bf30131cbdda75ca2
-README.zh.md: b10183496479249346da5da808f5ab3b6d2eef67
+README.md: 099da3ae3d4e2b45507fd18d279650ef0525f36a
+README.zh.md: dc7fa5f78ea758cea75e86eefb0c06ebe92e61d2