feat(apps): add impact-seg-konfai segmentation CLI wrapper

[vboussot]

📚 Stacked on #17 (pr/modif-core). The diff is against pr/modif-core.

Summary

Adds impact-seg-konfai, a thin, pip-installable CLI wrapper that runs the published IMPACT-Seg models through KonfAI Apps. These are 2.5D residual-encoder U-Nets that segment CBCT, MR, and CT into a single consistent label space; the bundle gives them a segment / eval / uncertainty / pipeline command surface without users hand-writing configs or resolving Hugging Face repos manually. Purely additive: a new apps/impact_seg/ bundle built on the konfai_apps public API introduced earlier in the stack — no core or konfai-apps changes.

What changed

New app bundle — apps/impact_seg/ (excluded from the konfai wheel, like the other apps/* wrappers).

• CLI (impact_seg_konfai/cli.py) — builds main via konfai_apps.cli.build_app_cli:
  • resolve_app pins the app id to VBoussot/ImpactSeg:<model> (IMPACT_SEG_KONFAI_REPO = "VBoussot/ImpactSeg"), so the model is chosen by a single positional model argument (_add_selection); an unknown name is reported at app-resolution time.
  • _add_infer_knobs adds --ensemble, --tta, and --mc (all int, default 0); resolve_infer returns the infer kwargs {"ensemble", "ensemble_models": [], "tta", "mc"}.
  • infer_command="segment" renames the inference operation, giving sub-commands segment / eval / uncertainty / pipeline.
• Packaging (pyproject.toml) — distribution impact-seg-konfai with dynamic = ["version", "dependencies"]; setuptools_scm rooted at the repo root (root = "../..", tag_regex = "^v(?P<version>.*)$", local_scheme = "no-local-version"); registers the impact-seg-konfai = impact_seg_konfai.cli:main console script.
• Version/deps resolution (setup.py) — _release_version() reads Version from PKG-INFO when building from an sdist, otherwise falls back to setuptools_scm.get_version, then pins install_requires=["konfai==<v>", "konfai-apps==<v>"] to lock the wrapper to matching core and apps releases.
• Housekeeping — impact_seg_konfai/__init__.py (package docstring), .gitignore, and Apache-2.0 LICENSE (SPDX header on cli.py).
• README.md — documents the body model (11 anatomical labels across CBCT/MR/CT), the four sub-commands and all flags, PyPI/source installation, automatic model download from VBoussot/ImpactSeg, and a Performance & VRAM section (auto batch-size selection via vram_plan, overridable with --patch-size / --batch-size).

Testing

No tests are added or modified — git diff --name-only pr/modif-core..pr/seg touches only apps/impact_seg/* (7 files, +468). The CLI is a declarative wrapper over konfai_apps.cli.build_app_cli, which already exists on the base branch and is covered by the konfai-apps/tests suite; the new surface is limited to the callbacks and packaging metadata above.

Review notes

• Stacked PR — base is pr/modif-core (feat(core): registration primitives + app patch/batch & asset plumbing #17); review only the apps/impact_seg/ diff.
• Risk — additive only; no konfai or konfai-apps sources change, so there is no regression surface for existing workflows.
• Points to verify — the ==<v> pinning in install_requires ties each wrapper release strictly to matching konfai / konfai-apps versions (intended; worth a sanity check against the tag scheme), and resolve_infer passes an empty ensemble_models: [], deferring to the bundle's app.json defaults when --ensemble / --tta / --mc are left at 0.