test: move the Postgres tests off the table other projects write to

Seven cases wrote straight into the shared table and told their rows
apart by a call_id prefix. Reading was never the problem; the prefix
did that correctly, and it was built for concurrent runs. What it could
not do was stop those writes and deletes from moving a row count that
another test was watching, which is how issue #18 turned red.

They now write into sandbox schemas, which also ends the orphan rows a
killed run used to leave in there. Six fixtures collapse into factory
calls; what they yield is unchanged, so the cases that consume them did
not have to be touched, which is what makes them worth anything as a
check on the move.

Two of the seven kept something. The pool footprint case needs a unique
application_name, since connections are an instance-wide resource that
schema isolation does not reach, so it generates its own uuid instead
of borrowing the run prefix. And the frozen-columns case was querying
information_schema without a schema filter, so any leftover table of
the same name anywhere in the database could fail it: the file already
knew this, in a comment explaining why another fixture cleans up so
carefully. It now filters, and gets checked against a leftover table
planted on purpose.

The gate that keeps the literal out of tests/ is a smoke alarm, not
proof. Concatenation and parameterised queries walk straight past it.
The isolation is the factory withholding the admin connection and the
script running as a role with no grant.

Makefile

@@ -1,21 +1,34 @@
-.PHONY: install test lint format check ci wiki wiki-check
+.PHONY: install test lint format check ci wiki wiki-check shared-table-gate
 
 ENV := PolyGateway
 
+# 集成测试触碰共享表 llm_calls 的字面量门(issue #18)。
+# 这道门是**烟雾报警器,不是隔离证明**: 它拦不住 f"{schema}.{table}" 拼接、
+# 参数化查询,或不带限定名的 DELETE 配上 admin 的默认 search_path。真正的隔离
+# 来自两处——沙箱工厂不把管理连接交给用例,以及清理脚本以无权角色运行。
+# 留着它是因为字面量回归最常见、也最便宜拦。
+shared-table-gate:
+	@if grep -rn --include='*.py' 'public\.llm_calls' tests/; then \
+		echo ""; \
+		echo "错误: 集成测试不得触碰共享表(见上面的命中行)。"; \
+		echo "改用 tests/integration/conftest.py 的 pg_sandbox 工厂;注释里提到它请写「共享表 llm_calls」。"; \
+		exit 1; \
+	fi
+
 install:
 	conda run -n $(ENV) pip install -e ".[redis,postgres,structured,dev]"
 
 test:
 	conda run -n $(ENV) pytest tests/ --cov=src/polygateway --cov-report=term-missing
 
-lint:
+lint: shared-table-gate
 	conda run -n $(ENV) ruff check src/ tests/ --fix
 	conda run -n $(ENV) lint-imports
 
 format:
 	conda run -n $(ENV) ruff format src/ tests/
 
-check:
+check: shared-table-gate
 	conda run -n $(ENV) ruff format --check src/ tests/
 	conda run -n $(ENV) ruff check src/ tests/
 	conda run -n $(ENV) lint-imports