Remove upstream-only workflows; retarget typecheck to main (#14)

Removes 30 inherited workflows from anomalyco/opencode that don't apply to
this fork (Discord webhooks, marketplace publishing, SaaS deploy infra,
community moderation bots, OPENCODE_API_KEY-gated automations, Nix flake,
Storybook). All would either fail loudly on missing secrets or remain
inert because they target dev branch / upstream repo.

Removes test.yml because it runs upstream's full unit + Playwright e2e
against packages we do not ship (opencode, @opencode-ai/app).

Retargets typecheck.yml from dev to main and switches off Blacksmith
self-hosted runners. Calls 'bun typecheck' which is already filtered to
our packages via the root package.json command.

Author: Alezander9