Say How Each Measured Requirement Actually Fails

spec/host-tools.json

@@ -50,7 +50,7 @@
             "probes": [["python3", "--version"], ["py", "-3", "--version"]],
             "pattern": "Python (\\d+(?:\\.\\d+)*)",
             "minimum": "3.13",
-            "why": "Every script here is standard library only, so a bare interpreter is enough and no package floor exists. The floor is the toolchain target rather than a measured breakage one version below it, which is the one entry here that reads that way and says so rather than implying a defect nobody found. pyproject.toml sets ruff target-version to py313 and mypy python_version to 3.13, so what those tools report describes 3.13 and describes no other interpreter, and a run below the floor is unverified rather than known broken. Neither tool runs in CI, which gates the standard-library script tests and the prose and repo gates and nothing else, so this floor is a configuration choice rather than an enforced result, and a host failing it has no CI failure to point at. Two hard requirements are measured and both sit lower: str.removeprefix and str.removesuffix need 3.9 and are called in spec/audit.py and scripts/prose_lint.py, and datetime.UTC needs 3.11 and is used in spec/audit.py, scripts/pr_review.py and their tests. Those are what an older interpreter actually fails on, as an AttributeError at the call rather than at startup. The name rather than the version is what differs per platform, which the second probe covers.",
+            "why": "Every script here is standard library only, so a bare interpreter is enough and no package floor exists. The floor is the toolchain target rather than a measured breakage one version below it, which is the one entry here that reads that way and says so rather than implying a defect nobody found. pyproject.toml sets ruff target-version to py313 and mypy python_version to 3.13, so what those tools report describes 3.13 and describes no other interpreter, and a run below the floor is unverified rather than known broken. Neither tool runs in CI. What CI does run is markdownlint, cspell, actionlint and editorconfig-checker, the registry and spec validation, the script self-tests, and the repo and prose gates, and no Python linter or type checker among them. So this floor is a configuration choice rather than an enforced result, and a host failing it has no CI failure to point at. Two hard requirements are measured, both sit lower, and they fail differently. str.removeprefix and str.removesuffix need 3.9, and each is called where the tree actually calls it: removeprefix in scripts/prose_lint.py and spec/audit.py, removesuffix in spec/audit.py alone. An older interpreter starts, runs, and raises AttributeError when it reaches one. datetime.UTC needs 3.11 and arrives through a module-level from datetime import UTC in spec/audit.py, scripts/pr_review.py and its tests, so an older interpreter raises ImportError before any of those modules run at all. Which mode a host sees is decided by the script it runs rather than by the interpreter alone: spec/audit.py carries both and fails at import, scripts/pr_review.py carries only the import and fails the same way, and scripts/prose_lint.py carries only the call and therefore starts, runs, and fails partway through. The name rather than the version is what differs per platform, which the second probe covers.",
             "source": {
                 "linux": "Whatever the platform provides at or above the floor, since the scripts need an interpreter and no packages, so no distribution or build is pinned here.",
                 "macos": "Whatever the platform provides at or above the floor, on the same reasoning as Linux.",