Fix/issue 7208 Improve connection error handling and proxy support

[su0as]

Summary
Addresses issue #7208, improving error handling of model/network responses and respecting IDE proxy settings.

Changes
VS Code extension:
◦ Auth: WorkOsAuthProvider now respects VS Code proxy and SSL settings (http.proxy, http.proxyStrictSSL) and uses the shared fetch that supports proxies.
◦ YAML: Register JSON schema for YAML only if the Red Hat YAML extension is present (prevents noisy errors).
◦ Manifest: Authentication provider declared to eliminate provider declaration warnings.

GUI:
◦ Error dialog updated to provide actionable guidance for connection/network issues (mentioning proxy settings).

Rationale/Impact
• Reduces failures in proxied/enterprise environments, improves user guidance, and removes spurious warnings. Localized and low-risk; no infra or dependency changes.
• Repro/Verification
• Configure a proxy in VS Code or via environment settings; simulate blocked control-plane access to see improved UX and proxy-awareness.
• Type checks and lint pass. Some tests require API keys; those remain skipped/expected. E2E harness shows environment-specific flakiness but unrelated to these changes.

Notes
• No new dependencies; uses existing @continuedev/fetch.
• Backwards compatible and easy to rollback.

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Summary by cubic

Improves connection error handling and proxy support in the VS Code extension and GUI to reduce failures behind corporate proxies and provide clearer guidance. Addresses #7208.

• Bug Fixes
  • VS Code: WorkOsAuthProvider now respects http.proxy and http.proxyStrictSSL and uses shared fetch with proxy support.
  • VS Code: Register YAML schema only if the Red Hat YAML extension is installed to avoid noisy errors.
  • VS Code: Declare the "continue" authentication provider to remove provider warnings and enable onAuthenticationRequest activation.
  • GUI: Connection error dialog adds actionable tips (proxy settings, invalid apiBase) with quick actions to reconfigure and retry.

[RomneyDa]

@su0as note failing tests

[RomneyDa]

Is this the standard yaml extension?

[su0as]

Yes. redhat.vscode-yaml is the standard Red Hat YAML extension. I added an inline comment to make that explicit.

[RomneyDa]

I think most users seeing a network error would not have proxy configured, and this might point users to the wrong place. In the majority of cases it is probably internet flake or no internet connection. That is, once the proxy is configured correctly, then it should generally work, and it's nice to have configuration errors but a low proportion of users use proxies

[su0as]

Adjusted. It now leads with internet flake/outage and invalid apiBase; proxy guidance is last and phrased as “If you’re behind a corporate proxy, verify proxy settings in your IDE (http.proxy, http.proxyStrictSSL) or your NO_PROXY configuration."