feat: pwm-tui ratatui demo proving the real checkpoint locally, no Docker

[AbdelStark]

Closes #200.

What this adds

pwm-tui, an unpublished ratatui crate that runs the exact ./demo/run-real.sh path natively, with no Docker, as a live terminal UI with seven stages (FETCH, EXPORT, LOAD, INFER, COMMIT, VERIFY, TAMPER), per-stage detail panels (download gauges, exporter substage progress, op histogram, commitment table, verdicts), a toggleable raw log pane, a metrics footer, NO_COLOR support, and a panic hook that restores the terminal.

cargo run -p pwm-tui --release                       # first run downloads ~77 MiB + the torch env
cargo run -p pwm-tui --release -- --offline          # warm cache: no network at all
cargo run -p pwm-tui --release -- --headless --json  # CI mode: plain log + JSON summary
cargo run -p pwm-tui --release -- cache path|ls|clear

Cache management

• Precedence: --cache-dir > PWM_CACHE_DIR > platform default (~/Library/Caches/ProvableWorldModel on macOS, ~/.cache/provable-world-model on Linux).
• Every external asset (checkpoint, episode parquet, episode mp4) is sha256-pinned in source; a hit means the cached file reproduces its pin, a corrupt entry is deleted and re-fetched, a rotated upstream fails closed. This also closes the unpinned-curl gap in the existing demo path.
• Downloads go through curl (already the Docker path's downloader; keeps the Rust tree free of a TLS stack the license gate would reject) into atomic .part files with resume and a per-file lock.
• The exported bundle is cached under a key derived from the asset pins plus the sha256 of the Python exporter sources, so editing the exporter invalidates bundles automatically. A warm bundle hit skips Python entirely; repeat runs are pure Rust and take about a second.
• --offline fails fast on a cold cache, --refresh re-downloads, --re-export forces stage 1, cache clear only deletes the cache's known subdirectories and requires --yes.

Shared computation, no drift

build_predictor_report and PredictorReport moved from bin/pwm.rs into pwm_testkit::report with phase callbacks; the pwm CLI and the TUI now render the same single load -> prove -> verify -> tamper computation. The exporter gained an LEWM_JSON_EVENTS NDJSON event mode (pretty log moves to stderr; the Docker path is byte-identical without the variable) and LEWM_PUSHT_PARQUET / LEWM_PUSHT_MP4 local-path overrides so stage 1 runs network-free.

Parity with the Real E2E gate (verified locally)

Cold run on this branch, same conditions the CI gate enforces:

• accepted: true, weights_root_source: "export-bundle"
• weights_root 3733fc82…, model 59cc509a…, quant a6fab519…, z_out_head [0, 7, -40, -11, -10, 3]: bit-identical to the Docker --profile real run
• float_error 0.282924 <= float_tolerance 0.282925
• tamper pass rejected with FreivaldsCheckFailed { op_id: 2 }
• warm --offline run: FETCH all cache HITs, EXPORT skipped (bundle cache), exit 0; corrupt-entry re-fetch and cold---offline fail-fast both verified

Tests and gates

• 18 unit tests in pwm-tui (cache hit/miss/corrupt, pinned fetch over file://, offline fail-fast, rotated-pin fail-closed, event parsing, app state folds, TestBackend render assertions), 2 in pwm_testkit::report, a new stdlib-only Python event-stream test wired into check-local.sh full.
• check-local.sh quick green; cargo deny check green (documented ignore for the informational RUSTSEC-2024-0436 paste advisory: demo-only via ratatui 0.29, since ratatui 0.30 requires Rust 1.88 above the pinned MSRV 1.85, with instability pinned to 0.3.7 in Cargo.lock for the same reason); MSRV 1.85 workspace build green; rustdoc -D warnings green; release --ignored suite and mutation gate green.
• New opt-in TUI Smoke workflow (manual + weekly): cold headless run asserting the four parity conditions from the JSON summary, warm offline run asserting the bundle-cache skip, and the cache subcommands.

Follow-ups (out of scope)

• VERIFY from a disk-serialized artifact (explicit two-party handoff) once PredictorArtifact has a decode path.
• P1 rollout / P2 planning visualization in the TUI.