feat(docker): support a multimodal projector via --mmproj

Vision-capable GGUFs need a separate projector (mmproj) that maps image
embeddings into the text model's space. Add `mmproj` and `mmproj_offload`
as config keys and CLI overrides, and pass them through to llama-server.

The projector path resolves under hf_home exactly like model_path, so it
is covered by the existing read-only mount. validate_model_path() now also
checks the projector, which means --change rejects a missing one *before*
it removes the running container.

--no-mmproj-offload is suppressed when no projector is configured, since
llama.cpp rejects the flag on its own.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/test_docker_ops.py

@@ -178,6 +178,41 @@ def test_build_run_command_relative_model_path():
     assert cmd[idx + 1] == "/hf_home/qwen3/default.gguf"
 
 
+def test_build_run_command_no_mmproj_by_default():
+    cmd = build_run_command(make_cfg())
+    assert "--mmproj" not in cmd
+    assert "--no-mmproj-offload" not in cmd
+
+
+def test_build_run_command_mmproj_relative_path_resolves_under_hf_home():
+    cfg = make_cfg(mmproj="qwen3/mmproj.gguf")
+    cmd = build_run_command(cfg)
+    idx = cmd.index("--mmproj")
+    assert cmd[idx + 1] == "/hf_home/qwen3/mmproj.gguf"
+    # offload is llama.cpp's default, so the opt-out flag must stay absent
+    assert "--no-mmproj-offload" not in cmd
+
+
+def test_build_run_command_mmproj_absolute_path_passed_through():
+    cfg = make_cfg(mmproj="/abs/mmproj.gguf")
+    cmd = build_run_command(cfg)
+    idx = cmd.index("--mmproj")
+    assert cmd[idx + 1] == "/abs/mmproj.gguf"
+
+
+def test_build_run_command_mmproj_offload_disabled():
+    cfg = make_cfg(mmproj="qwen3/mmproj.gguf", mmproj_offload=False)
+    cmd = build_run_command(cfg)
+    assert "--no-mmproj-offload" in cmd
+
+
+def test_build_run_command_no_mmproj_offload_needs_mmproj():
+    # Without a projector the offload opt-out is meaningless and must not leak
+    # into the command line (llama.cpp would reject it).
+    cfg = make_cfg(mmproj="", mmproj_offload=False)
+    assert "--no-mmproj-offload" not in build_run_command(cfg)
+
+
 def test_format_command_for_display_quotes_properly():
     cmd = ["docker", "run", "--name", "has space"]
     out = format_command_for_display(cmd)