Cardano Updates

When `hydra-status-url` is provided, the action connects to the
hydra-github-bridge SSE endpoint for real-time build status updates
instead of polling the GitHub API. This dramatically reduces latency
from minutes (poll interval) to seconds (event-driven).

SSE mode features:
- One-shot check on cached status before opening the stream
- Event filtering by check-run name (ignores unrelated jobs)
- Process substitution to avoid subshell exit trap
- read -t 60 to enforce timeout during idle streams
- Periodic re-checks every 120s as CDN buffering safety net
- Graceful fallback to poll mode on connection failure

Without `hydra-status-url`, the action behaves exactly as before
(pure GitHub API polling with exponential backoff).

Copyright (c) Moritz Angermann <[email protected]>, Input Output Group.
SPDX-License-Identifier: Apache-2.0

When `hydra-status-url` is provided, the action connects to the
hydra-github-bridge SSE endpoint for real-time build status updates
instead of polling the GitHub API. This dramatically reduces latency
from minutes (poll interval) to seconds (event-driven).

SSE mode features:
- One-shot check on cached status before opening the stream
- Event filtering by check-run name (ignores unrelated jobs)
- Process substitution to avoid subshell exit trap
- read -t 60 to enforce timeout during idle streams
- Periodic re-checks every 120s as CDN buffering safety net
- Graceful fallback to poll mode on connection failure

Without `hydra-status-url`, the action behaves exactly as before
(pure GitHub API polling with exponential backoff).

Copyright (c) Moritz Angermann <[email protected]>, Input Output Group.
SPDX-License-Identifier: Apache-2.0