feat(competition): submission preflight go/no-go with per-benchmark gap-to-king

[galuis116]

What does this PR do?

summarize_competition (#397) tells a miner the composite score-to-beat, but not whether their own run clears it, nor where it falls short. The competition is composite: pr_eval approves only when the mean of the per-benchmark scores clears the reigning best_composite_score by win_margin. So a miner needs to turn their own per-benchmark scores into that same composite and compare — before spending a PR.

How

Add trinity.competition_preflight: given the loaded leaderboard + a miner's {benchmark: score}, it

• computes the composite the same way pr_eval does (mean over the competition's declared benchmarks, an unscored board counting as 0.0);
• decides go/no-go against king + win_margin and reports the exact gap to close;
• reports the per-benchmark delta versus the reigning king and the weakest board, so the miner sees which benchmark is dragging their composite down.

scripts/preflight_composite.py renders it and exits non-zero when the submission would not win:

$ preflight_composite.py --score math500=0.90 --score mmlu=0.90 --score livecodebench=0.75
- composite 0.8500 vs score-to-beat 0.9200 (king alice): would NOT win ❌
- shortfall: +0.0700 to close
| benchmark | my score | vs king |
| livecodebench | 0.7500 | +0.0500 |
- weakest board (improve here first): livecodebench (0.7500)

Scope

Pure stdlib — no torch, no network. New module + script + 10 offline tests; the substantive change touches no existing file. Companion to the merged competition-object toolkit (#384 integrity, #387 standings, #397 score-to-beat).

Note on CI / the analysis/init.py change in this diff

main currently has unresolved git merge-conflict markers in src/trinity/analysis/__init__.py (a botched merge → the package is invalid Python, so ruff/import fail on every branch). This PR carries the identical repair only to keep its own CI green — it's the same fix as the in-flight #402 / #405 and drops out on rebase once main is green. The preflight feature itself is the real content.

Duplication note

Verified against every open PR's file list: competition_preflight.py + its CLI/tests are unique to this PR; the only overlap is the shared analysis/__init__.py CI-unblock (transient).