fix(docker): a container's memory is its processes' own; file cache shown on its page (#6030)

The agent sent Docker's working set (usage less inactive_file), which still
counts recently used file cache. A file-heavy container with no limit read
191 GB while its processes held 2.2 GB, and the host's own figure, which
already leaves cache out, disagreed with it.

Agent 1.23.0 sends mem_used_bytes / mem_used_pct (anon + shmem, so
Postgres's shared buffers count; v1: rss + shmem) and mem_cache_bytes
apart. The new names keep the two meanings apart in history and in learned
normals: docker_013 renames the columns, clears the old values and adds
mem_cache_bytes. The Docker page, swarm by-node sums, Busiest Containers,
container detail, normals and the MCP tools all read the new figure. File
cache is shown only on the container's page and in get_container.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

plugins/docker/models.py

@@ -29,10 +29,14 @@ class DockerContainer(Base):
     # running | stopped | paused | exited | dead
     cpu_pct: Mapped[float | None] = mapped_column(Float, nullable=True)
     # BigInteger: a container's memory usage/limit routinely exceeds 2^31 bytes
-    # (~2.1 GB), which overflows int4 and fails the insert.
-    mem_usage_bytes: Mapped[int | None] = mapped_column(BigInteger, nullable=True)
+    # (~2.1 GB), which overflows int4 and fails the insert. Used is what its
+    # processes hold (anon + shmem); file cache is kept apart, since the kernel
+    # gives it back when the host needs it (#6030). used_pct is of the limit,
+    # which is the host's RAM when none is set.
+    mem_used_bytes: Mapped[int | None] = mapped_column(BigInteger, nullable=True)
     mem_limit_bytes: Mapped[int | None] = mapped_column(BigInteger, nullable=True)
-    mem_pct: Mapped[float | None] = mapped_column(Float, nullable=True)
+    mem_used_pct: Mapped[float | None] = mapped_column(Float, nullable=True)
+    mem_cache_bytes: Mapped[int | None] = mapped_column(BigInteger, nullable=True)
     restart_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
     ports_json: Mapped[str] = mapped_column(Text, nullable=False, default="[]")
     # JSON: [{"host_port": 8080, "container_port": 80, "protocol": "tcp"}]