e770d573

By: ValentinHirschi <valentin.hirschi@gmail.com>

Symbolica Arc MRE: review fixes, layout control, interleaved re-measurement

- main.rs: pins and reports the cache-line offset of the shared context and
  variable-map ArcInner (--ctx-offset/--map-offset), per-thread asserts that
  each variant uses the contexts it claims, --ahash-source thread-local
  (ahash set_random_source), perf counters limited to the timed loop
  (perf stat --control fifo), glibc version, Linux cfg guards.
- examples/minimal.rs: 100-line version of the reproducer.
- Cargo.toml: default dependency is crates.io symbolica =3.0.0 (tested
  offline); dev/local routes documented.
- scripts: process starts on the first run CPU, arena_max, median tables,
  user-GHz column, near/far wording, per-EXTRA file names.
- results/socket1-20260928T133455Z-fix: sweep, layout A/B, profiles, patch
  A/B (pristine dev 445b882d vs 1a+2, proposed.diff, padding; interleaved,
  3 repeats) and map-offset follow-up; NOTES.txt.
- README rewritten: layout dependence, corrected nvars load-chain reading
  (skid), 1b downgraded to a design direction with open questions, ablation
  of the patch, ahash app-side workaround, requirements for other hosts.
- PROVENANCE.txt for the first session (v1 rename, uncontrolled layout).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>