refactor(sam): converge 4 SAM integrations — v1 scripts / v2 layers / v3 sam3.py / EVF-SAM

[yha9806]

Problem

Vulca currently has 4 parallel SAM integrations accreted over 5 days (2026-04-15 to 2026-04-20), each with its own dependency tree, with no convergence:

Path	SAM gen	Module	State
`scripts/claude_orchestrated_pipeline.py`	v1 (2023)	`segment_anything` + `sam_vit_l` checkpoint	Hardcoded `/tmp/sam_vit_l.pth`, no env override
`src/vulca/layers/sam.py`	v2 (2024)	`sam2.build_sam` + `SAM2ImagePredictor`	HF Hub `facebook/sam2.1-hiera-small`
`src/vulca/layers/sam3.py`	v3 (2025)	`transformers.Sam3Model`	Requires `transformers>=4.50` — conflicts with EVF-SAM `transformers==4.49` pin
`scripts/_evfsam_common.py`	EVF-SAM	text-prompted, vendored fork	Forces transformers pin to 4.49

Why this matters

Surfaced 2026-04-24 γ Scottish showcase: `/decompose` mode="orchestrated" hit cascading issues:

1. `No module named 'segment_anything'` (MCP Python 3.11 env didn't have v1 SAM dep — pyproject [sam] extra was for v2)
2. `cannot import name 'ImageNetInfo' from 'timm.data'` (timm 0.6.13 too old for transformers 4.49 timm_wrapper; but torchscale pins timm=0.6.13)
3. After install, MCP Python import cache held failed-import state — required full session restart

End user wasted ~30 minutes diagnosing dep chain that should have been a single `pip install`. Plus 1.2GB SAM v1 checkpoint download because the system can't probe / reuse the EVF-SAM weights or FastSAM-s.pt the user already has on disk.

Proposed convergence

v0.18.0 target (not v0.17.12 — too large for rollup release):

1. Retire `scripts/claude_orchestrated_pipeline.py` — merge into `src/vulca/layers/orchestrated.py` so the orchestrated mode lives inside the package, gets pyproject `[sam]` extras correctly, and is unit-testable.
2. Migrate orchestrated mode to SAM v2 — already-imported `src/vulca/layers/sam.py` works, no need for parallel v1 path. Eliminates segment-anything dep + /tmp checkpoint.
3. Add `VULCA_SAM_CHECKPOINT` env var (transitional, while v1 path exists) — let user point at any pre-deployed checkpoint instead of hardcoded `/tmp/sam_vit_l.pth`.
4. Startup capability probe — MCP server logs which SAM/loader paths are functional at boot. Agent can introspect `get_capabilities()` to choose mode intelligently.
5. Unpin transformers OR sandbox EVF-SAM — current pin to 4.49 blocks SAM3 adoption. Either upgrade EVF-SAM fork to 4.50+ (upstream support TBD) or run EVF-SAM in subprocess venv to isolate.

Blockers

• EVF-SAM fork is not upstream-tracked; transformers upgrade may require maintaining our own fork
• SAM3 is GPU-only in current Hugging Face bindings; MPS support unclear

Scope

v0.18.0 target. Requires independent brainstorm session — large enough that this issue is a placeholder to track the design discussion. Do not attempt within v0.17.12 rollup.

Surfaced from

2026-04-24 γ Scottish showcase Part 1 session.