Contract follow-up: NSIS host=LV2020 only + .lvcontainer-derived docker versioning/job metadata

[svelderrainruiz]

Summary

Implement container/version signaling and host/runtime separation for NSIS and build-spec execution.

Required policy changes

1. Host OS NSIS path must only use LabVIEW 2020.
2. Any LabVIEW version other than host-2020 must run via Docker.
3. Docker image version must be derived from labview-icon-editor/.lvcontainer at clone time.
4. .lvcontainer raw text must be imprinted into the job name.
5. Derive and imprint bitness in the job name to indicate which LabVIEW bitness the container used for build-spec (PPL) execution.
6. Add a placeholder lane for source-distribution build-spec execution (similar style to Apply VIPC).

Acceptance criteria

• Workflows enforce host-only LV2020 for NSIS installer path.
• Non-2020 build-spec lanes resolve container tag from cloned labview-icon-editor/.lvcontainer.
• Job names include .lvcontainer text and derived bitness.
• PPL build-spec lane explicitly reports container bitness used.
• Source-distribution placeholder lane exists and emits deterministic status/artifacts (Apply VIPC-style contract).
• Contract tests cover these rules and fail on regressions.

Notes

Opened as requested to track this as a dedicated change set rather than mixing into current gate stabilization/merge lane.