fix(fixtures): repair the cancel-fixture abort error placement; exempt pwsh-local coverage on pwsh-less hosts

The hand-edit in 348ab41151 put the seq-17 abort error inside the tool-result
message and dropped a closing brace, breaking every JSONL consumer; tool-calls.ts
appends 'error' as a data-level sibling of 'message' (the seq-19 shape), so the
fixture now matches the emitter.

Coverage: pwsh-local's executor suites self-skip without a real pwsh, which left
per-file 100% unreachable on pwsh-less contributor hosts (mirror of the existing
windowsCoverageExclusions contract). A PATH-only probe exempts only
pwsh-local/src/index.ts; CI runners ship pwsh and still enforce the full bar.
docs/testing.md (+zh, pairing re-recorded) names the prerequisite; the testing.md
budget rises 1120->1150 because the coverage-gate contract genuinely grew.

docs/testing.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write docs/testing.md
-testing.md: d460d9ba76eab84b79e8c66454325d03d7c5908e
-testing.zh.md: 821e49b6593b924e754d5ed0d588dd1b5b566051
+testing.md: 5e766bb684d9d76a1c9e854a2aef95796a31ec12
+testing.zh.md: 21b3f98e9ddbbb6f77621cff9ce206ae17125bc3