#977 --check prints [ok] for below-floor RAM and a misleading 'This PC can run Strata' verdict

Beschreibung

## Summary

`setup.sh --check` (and Windows `START-HERE.bat --check`) prints the RAM line with `[ok]` even when RAM is **below the 32 GB floor the smallest model needs**, and the final verdict is still "This PC can run Strata" — directly contradicting the per-model "does not fit" list printed right above it.

## Environment

- WSL2 Ubuntu 26.04 on a 32 GB Windows host; WSL exposes 16-27 GB depending on host load (driver 617.14, RTX 3060 12 GB + RTX 2080 8 GB)
- Fresh clone of main @ `6f32ec0`

## Verbatim output

```
[ok] GPU: NVIDIA GeForce RTX 3060, 12.0 GB VRAM, compute capability 8.6, driver 617.14
[ok] RAM: 16 GB (less than the 32 GB the smallest model needs)
[ok] CPU: Intel(R) Xeon(R) CPU E5-2698 v3 @ 2.30GHz (AVX2)

Q2_0 needs ~48 GB RAM: does not fit
IQ2_XS needs ~48 GB RAM: does not fit
IQ3_XXS needs ~60 GB RAM: does not fit
IQ3_S needs ~62 GB RAM: does not fit
IQ1_M needs ~32 GB RAM: does not fit
UD-Q4_K_XL needs ~48 GB RAM: does not fit
UD-IQ4_XS needs ~48 GB RAM: does not fit

This PC can run Strata. Run it again without --check to install.
```

## Expected

- RAM line should be `[X]` (or a warning) when below the floor, mirroring the GPU failure style
- Final verdict should reflect that **zero model sizes fit**, e.g. "This PC cannot run Strata yet: needs 32 GB RAM for the smallest size" instead of "This PC can run Strata"

## Related ergonomics note

On Windows, the `--check` batch `pause`s on failure and exits with code 0, so scripted/headless checks can't detect the failure via exit status. A non-zero exit on failed checks would make agent-driven installs (docs/AI_SETUP.md workflow) reliable.

Context: we ran the full check + test suites on this box as part of an install evaluation (details can be provided; the RAM reading itself also varies under WSL's dynamic memory, which makes the `[ok]`-regardless behavior more confusing).