Add fast_forward mode to CC:Ladder

[john-b-yang]

Optional CC:Ladder mode that skips playing rungs the climber's carried-over bot already dominates — faster eval, same "highest rung reached" north-star metric.

Usage (nested under ladder_rules, off by default)

ladder_rules:
  min_round_wins: 2
  win_last_k: 0
  fast_forward:
    enabled: true
    min_sim_win_rate: 0.9   # skip a rung if the bot wins >= 90% of its round-0 sims

How it works

• At each rung, a round-0-only probe (rounds: 0 PvpTournament) runs the carried-over bot vs the opponent.
• If the climber's share of round-0 sims (ties count as non-wins) ≥ min_sim_win_rate, the rung is cleared without edit rounds, recorded as ladder_advancement.fast_forwarded: true.
• Anything not cleanly won plays in full under the normal ladder_rules — so it's safe under non-transitive matchups and never skips a rung it would lose.
• Rung 1 is identical-code (~coin flip), so it never fast-forwards; the climber always earns the first rung.

Interactions

• Resume-safe: fast-forwarded rungs make no code change (no round tags), so _scan_resume keeps the carry-over seed from the last played rung.
• Summary gains rungs_fast_forwarded.

Validation

enabled (bool, required if block present); min_sim_win_rate (number in (0.5, 1.0], required when enabled).

Notes

• No CLI change — config-only.
• Verified Docker-free: validation, the fast-forward metadata record, and the resume interaction. The probe itself exercises via Docker at runtime.
• Builds on the resume feature (Add resumable CC:Ladder runs (ladder run --resume) #118, merged).

[Muhtasham]

LGTM!

[john-b-yang]

tysm for review @Muhtasham!! Will dm you and sync on the status of the changes i've been making the past couple days :)