chore(scripts): add scripts index and archive one-shot scripts (#4822)

chore(scripts): index scripts/ and archive 29 one-shot scripts

backlog#1153 infra-13. scripts/ had 80+ unlabelled top-level entries
mixing CI gates with finished one-shot issue-validation scripts.

- scripts/README.md — one index row per entry with status
  (ci-gate / dev-tool / archived), purpose, and wiring; subdirectories
  get one row each. run_scanner_benchmarks.sh is annotated
  "disposition owned by backlog perf-10" and deliberately untouched.
- git mv 29 confirmed-stale one-shot entries to scripts/archive/:
  11 issue-scoped validation/perf-capture scripts, the 5-script
  backlog#706 large-PUT breakdown family, the 4-file GET-optimization
  stress suite, 2 gt1g one-shots, and 7 other orphaned one-shots.
  Evidence: a whole-tree boundary-aware reference census showed zero
  references from CI/Makefiles/docs/code for every moved entry (or
  references only from other scripts inside the same archived set);
  re-run after the move shows zero dangling references.
- docs/testing/README.md links the index.

Moves only — no script content changed.

docs/testing/README.md

@@ -63,6 +63,10 @@ Layer notes:
 - **Benchmarks** — Criterion benches live under each crate's `benches/`. They
   are not a gate; run them locally to compare before/after on a specific crate.
 
+Script inventory: every entry under `scripts/` — including the runners above —
+is indexed in [`scripts/README.md`](../../scripts/README.md) with its status
+(ci-gate / dev-tool / archived) and wiring.
+
 ### Security advisory regression tests
 
 Fixed GHSA advisories map to named, discoverable regression tests. The