v6: Simplify the status bar and make the connection indicator functional

[trevor-scheer]

Summary

• The bottom status bar drops the plugin count, the UTF-8 encoding label, and the GraphQL language label. None of them told the user anything useful; they just made the bar look like a code editor's chrome.
• The connection dot reflects real state instead of just "schema loaded or not." It's amber while introspection or a request is in flight, green once a schema is loaded, red when the last introspection or request failed, and gray when nothing has happened yet. Each state has a matching text label and an accessible title on the dot.
• The types count stays as a plain readout ("142 types") once a schema is loaded. It's deliberately not clickable, so the status bar doesn't reach into the doc-explorer plugin.
• This doesn't cover full subscription-level status (an open subscription's live/closed state, tracked separately from a one-shot query). The dot derives from schema-load state plus the last request's fetch/error state, which handles the common cases without new transport plumbing.

Test plan

• Open GraphiQL. The status bar shows only a connection dot with a label and a types count, with no plugin count, UTF-8, or GraphQL.
• Before a schema loads, the dot is gray and reads "Idle".
• While the schema is loading, the dot is amber and reads "Connecting".
• Once the schema loads, the dot turns green, reads "Connected", and the types count appears.
• Run a query successfully. The dot stays green.
• Point the endpoint at something that errors (bad URL, malformed response). The dot turns red and reads "Connection error".
• yarn workspace @graphiql/react test passes.

Refs: #4219

[changeset-bot]

🦋 Changeset detected

Latest commit: b48f173

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 8 packages

Name	Type
@graphiql/react	Patch
@graphiql/plugin-code-exporter	Patch
@graphiql/plugin-collections	Patch
@graphiql/plugin-doc-explorer	Patch
@graphiql/plugin-explorer	Patch
@graphiql/plugin-history	Patch
@graphiql/plugin-query-builder	Patch
graphiql	Patch

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