test(web): fail the build when marketing copy drifts from shipped providers (#126)

The last three PRs all fixed the same class of bug. /credential-sharing
and README.md are hand-written copy; the providers they advertise are a
real registry in @logicsrc/plugin-credential-sharing. Nothing connected
the two, so the `team` provider shipped on 2026-07-13 and three weeks
later both surfaces still described a five-provider tool with no mention
of teams. The docs were right the whole time -- only the pages people
actually land on had gone stale, which is worse, because it reads as
"the product cannot do this" rather than as a documentation gap.

Assert it instead. For every provider in the registry, the Credential
Sharing section and the README must say something that counts as
advertising it. The registry's own `name` cannot be the proof -- `env`
is "Local .env file" and `team` is "LogicSRC Team Vault", neither of
which is how the copy reads -- so each provider declares its own
pattern, and a provider with no declaration fails too. That way adding
a provider forces a deliberate answer about the customer-facing copy.

Verified against the bug it is meant to catch: reverting the team copy
reproduces "These providers ship but /credential-sharing never mentions
them: team", and reverting the README line reproduces the same for
sh1pt and team.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

package-lock.json

@@ -148,6 +148,7 @@
         "sanitize-html": "^2.17.5"
       },
       "devDependencies": {
+        "@logicsrc/plugin-credential-sharing": "file:../../plugins/credential-sharing",
         "@playwright/test": "^1.57.0",
         "@types/node": "^24.10.1",
         "@types/react": "^19.2.0",