progress: indicatif bar in eigenvalue loop + per-case/seed banners

[sorcerer86pt]

Wires indicatif into both CPU and GPU eigenvalue power-iteration loops so long simulations no longer run silent. The new transport::progress::EigenProgress exposes three sinks:

• animated bar (TTY) — [████░░░░] 47/150 | k=1.00123 <k>=1.00098 +/- 64 pcm | ETA 2m13s
• per-batch eprintln (forced) — opt-in via OPEN_RUST_MC_PROGRESS=1
  when stderr is piped (cargo test
  --nocapture, CI, run_benchmark.ps1
  tee'd output)
• silent — default off-TTY behaviour, keeps
  sweep logs lean

Auto-hides under verbose=true so it doesn't fight with println! debug output.

Per-seed banners added to the ICSBEP integration tests (tests/icsbep_runs.rs::run_case_e2e_seeds and
tests/cuda_runs.rs::run_case_cuda_seeds) print
[icsbep] case -- seed N/M starting + elapsed-time done line around each seed; useful when single seeds take ≥400 s.

Python sweep (icsbep_sweep.py) gains a per-case banner [idx/total] case starting (Nseed x Bb x Ii x Pp) and per-seed banners inside run_case_multi_seed. run_benchmark.ps1 gains a -LiveProgress switch that sets OPEN_RUST_MC_PROGRESS=1 so per-batch lines land in the .log (since Tee-Object masks the TTY).

Tests:

• cargo test --lib --release: 438 / 438
• cargo test --lib --release --features cuda: 451 / 451
• tests/icsbep_runs::heu_met_fast_001_case_1_godiva smoke (PASS)
• python icsbep_sweep.py smoke on heu-met-fast-001 (PASS)