#3003 docs: the 0.1.44.1 changes no page told (start-crash #2324, setup re-run keeps size)

Description

Issue: Resolves # (documents #2324)

## Summary

Docs only - no code changed. Two 0.1.44.1 behaviours that no page told:

1. **Start-time crashes (#2324)**: an engine the OS ends at start (illegal instruction, access violation, the OOM killer, a missing DLL) is now treated as a crash, not a retryable GPU-runtime start. `TROUBLESHOOTING.md` and the `DETAILS.md` troubleshooting table had nothing about it.
2. **Setup run again over an installed model keeps its size**: `--setup` opens the size list with the installed size pre-selected, so Enter / `--yes` keep it; a re-run never silently moves a working install to the recommended (slower, larger) size.

## What changed

- `docs/TROUBLESHOOTING.md` - new section for the start crash (#2324): the exit words per OS, the AVX/AVX2/FMA/F16C flags, the `STRATA_ISA_FLOOR` pointer to "Older CPUs".
- `docs/DETAILS.md` - the matching row in the troubleshooting table.
- `docs/INSTALL.md` - the "Running setup again over an installed model?" bullet under "Setup's questions".
- `docs/AI_SETUP.md` - the same re-run rule for an assistant running setup non-interactively.

## Extra Notes

**Verified against the code on `main` (no GPU, no model):**
- #2324 "not retried": `serve/server.py` `engine_crashed` (L475) and the transient-start rule `... and not engine_crashed(rc)` (L562); `serve/test_server.py::StartCrashReported` runs 5/5 OK on Windows (3 skipped, Linux-only signals).
- re-run keeps size: `setup.py` `installed_size` (L2324); `tools/test_setup_rerun_size.py` 8/8 OK.

**Two accuracy fixes vs. the original branch commit, measured against `main`:**
- The AVX/AVX2/FMA/F16C flags are printed only on Linux - `cpu_isa_words()` reads `/proc/cpuinfo` alone, so on Windows/macOS the line names the illegal instruction by itself. The docs say that.
- No reference to the eval harness: `evals/` is not in `main`, so a pointer to it would be a dead link.

Docs only; the default path is untouched.