[CI] Parity: replace ROCm nightly with scheduled Preview

[ethanwee1]

Summary

• replace the retired nightly parity key with preview
• match the live daily rocm-preview linux-noble-rocm-preview-py3.12-mi350 jobs
• use the current 8/3/2 default/distributed/inductor fallback matrix

This clean replacement is based on current develop; it supersedes #3406, whose pre-reset history cannot merge without a force-push or unrelated-history merge.

Test plan

• Parse parity config JSON
• Compile download_testlogs
• Parse parity.yml as YAML
• Verify all 13 test jobs against scheduled pytorch/pytorch run 31344407133
• Run end-to-end Preview parity dispatch

Dependencies

Land this before the Preview auto-trigger update in #3397 and before retargeting the operational parity PRs.

Made with Cursor

Alignment landing order

This is the root dependency. After it lands, retarget the stacked PRs to develop in this order:

1. [CI] Parity: discover job topology from workflow YAML #3535 dynamic workflow/prefix/shard discovery
2. [CI] Parity: fix upstream job links #3536 canonical per-shard job URLs
3. [CI] Parity: classify newly observed ROCm skips #3523 consolidated classifier rules (independent base; may land earlier)
4. [CI] Parity: avoid variant-only trunk runs for ROCm Inductor #3559 variant-run filtering
5. [CI] Parity: skip missing configs without aborting report #3558 graceful missing-config handling
6. [CI] Parity: preserve partial reports on download failure #3557 partial-report preservation
7. [CI] Parity: use authoritative flaky-test summaries #3560 authoritative flaky attribution
8. [CI] Parity: resolve sha=latest on current develop #3556 latest-SHA resolution
9. [CI] Parity auto-trigger: collect scheduled architectures including Preview #3555 scheduled multi-architecture automation last

Validation: full Preview run 31506711303 and combined Preview+MI350 run 31507307756 both succeeded on matching SHA cf18dda7.