feat: support nibrun deployment

[massimoalbarello]

Stacked on #485 so this PR contains only the nibrun integration. It supersedes the nibrun-specific portion of #481.

Summary

• follow the nibrun runtime contract for external binding, persistent data, and the public HTTPS origin while preserving explicit OpenConnector overrides
• publish the smoke-tested Linux x64 executable to the dedicated nibrun-latest prerelease after successful main builds
• add a one-click deploy button and focused deployment documentation
• exercise nibrun environment handling in the standalone-binary smoke test, including public transit-file URLs

Dependencies

• feat: compile the server into Bun single-file executables #485 must land first
• the provider lazy-loader optimization mentioned in the review of feat: ship OpenConnector as a nibrun binary #481 has not been opened yet and should land before the nibrun deployment is enabled on main

This is a draft to prevent the stack from being merged into the #485 feature branch. Once its prerequisites land, it can be rebased or retargeted to main and marked ready.

Verification

• npm run fix-check
• npm test — 1,741 passed, 4 skipped
• npm run build:binary -- linux-x64
• standard and nibrun smoke tests against a native standalone binary
• workflow YAML and release-script syntax validation

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[massimoalbarello]

GitHub closed this PR when the stacked base branch was deleted after #485 merged, and closed PRs with deleted bases cannot be retargeted or reopened. The same deployment-only commit has been rebased onto main and reopened as #488.

[BlackHole1]

@massimoalbarello
I am adding logic related to provider lazy load, and I will submit the relevant PR later. You can wait for this PR to be merged before creating the feat nibrun PR.

Final goal: Support nibrun deployment, without hard-coding any nibrun-related logic in the existing code to ensure decoupling and independence.