test(python): pin the minimal composition's model-visible surface

The Python lane never compared what the minimal composition shows the
model: the mock model only asserted system-role messages, and the
advanced snapshot tokenizes the assembled system prompt and tool
schemas.

The sdk-minimal scenario now records model-visible.json — every model
request's advertised tool schemas verbatim and its message list, with
system and user text kept and assistant/tool payloads reduced to call
identity so the expected output replays on macOS and Linux. It excludes
the dynamic runtime-context snapshot, which the same composition emits
on macOS and not on Linux (#2488).

AGENTS.md and the testing policy name both SDKs as independent
projections of the agent loop, session lifecycle, and SessionEventMap.

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: 8ed81412a954bcd1d4b5d84eb4133ed081092764
-testing.zh.md: 5662db51847ba2f4e297d0bd3d4af0d024fa29fb
+testing.md: bef73983e48365f6655e4d4242f4f73223d971ed
+testing.zh.md: 7a5935165a335b4f3885092ef7b7b29f08f53c51