Add progressive recurrence SP8192 record submission

[wisebreadloaf]

Summary

• add a new record-track submission for the packed SP8192 progressive 3-layer recurrence variant
• document the verified 3-seed real 8xH100 SXM results, compliance details, and reproduction command
• include the exact packed train_gpt.py used for the submission-sized artifact

Results

• 3-seed TTT mean: 1.08061140
• Seed 42: 1.08050988 (15,992,388 bytes)
• Seed 999: 1.08177387 (15,996,018 bytes)
• Seed 1337: 1.07955046 (15,989,841 bytes)
• all three artifacts are under 16,000,000 bytes

Technique

• preserve the merged SP8192 + parallel residuals + QK-gain 5.25 + legal TTT stack
• replace the single-step full recurrence activation with a progressive schedule:
  • phase 1 at frac=0.35: one extra recurrence pass
  • phase 2 at frac=0.55: full 3-layer recurrence
• keep the packed LZMA wrapper so the submission remains under the size cap

Notes

• this PR packages the already-verified packed submission path into records/track_10min_16mb/...
• branch was prepared in a clean worktree to avoid mixing unrelated local changes from the main checkout