curl writes "000" to -w '%{http_code}' on a connection failure AND exits
nonzero. The previous fallback put the echo inside the command
substitution — both wrote, the captured value was "000000", and the
case statement's 000) arm didn't match, so dead hosts fell through to
PASS. Move the fallback assignment outside the substitution so the
captured value is exactly "000" and connection failures fail.
Also skip entries with an empty url field — those are placeholders
awaiting user config, not dead endpoints, and would false-fail.
Walks marketplace.json for vendored plugins, extracts http/sse MCP
server URLs from .mcp.json / mcp.json / plugin.json, and probes each
with HEAD then a JSON-RPC POST fallback. Fails on 404/410 and
connection errors; passes on auth/method errors (expected without
credentials). Runs on PR, daily schedule, and manual dispatch.
External (SHA-pinned) plugins are out of scope — their .mcp.json
isn't checked out here.
