ci: use --cov=./litellm so coverage paths resolve unambiguously in Codecov

pytest-cov treats --cov=<module-name> as a Python package and emits XML
paths relative to the package root, stripping the litellm/ prefix
(`proxy/proxy_server.py` instead of `litellm/proxy/proxy_server.py`).
Codecov's auto-prefix heuristic then drops every file whose basename is
ambiguous in the repo — `proxy_server.py` (3 copies under enterprise/),
`router.py` (2 copies), `utils.py` (20+), `main.py` (20+), `constants.py`
(2). The 11 highest-fix-rate hotspots have never appeared in Codecov.

Switching to --cov=./litellm treats the argument as a path, which makes
coverage.xml emit repo-relative paths (`litellm/proxy/proxy_server.py`).
Each path is unambiguous, so Codecov resolves all files correctly.

Verified locally: rerunning a single proxy_unit_tests test with
--cov=./litellm produced `filename="litellm/proxy/proxy_server.py"`,
`filename="litellm/router.py"`, and `filename="litellm/types/router.py"`
as distinct entries — exactly the disambiguation Codecov needs.

Touches every workflow that uploads coverage: the two reusable GHA
workflows (_test-unit-base.yml, _test-unit-services-base.yml),
test-mcp.yml, and all 14 invocations in .circleci/config.yml.

.github/workflows/_test-unit-base.yml

@@ -91,7 +91,7 @@ jobs:
             --reruns-delay 1 \
             --dist=loadscope \
             --durations=20 \
-            --cov=litellm \
+            --cov=./litellm \
             --cov-report=xml:coverage.xml \
             --cov-config=pyproject.toml
 

.github/workflows/_test-unit-services-base.yml

@@ -132,7 +132,7 @@ jobs:
               --reruns "${RERUNS}" \
               --reruns-delay 1 \
               --durations=20 \
-              --cov=litellm \
+              --cov=./litellm \
               --cov-report=xml:coverage.xml \
               --cov-config=pyproject.toml
           else
@@ -144,7 +144,7 @@ jobs:
               --reruns-delay 1 \
               --dist="${DIST}" \
               --durations=20 \
-              --cov=litellm \
+              --cov=./litellm \
               --cov-report=xml:coverage.xml \
               --cov-config=pyproject.toml
           fi

.github/workflows/test-mcp.yml

@@ -43,4 +43,4 @@ jobs:
 
       - name: Run MCP tests
         run: |
-          uv run --no-sync pytest tests/mcp_tests -x -vv -n 4 --cov=litellm --cov-report=xml --durations=5
+          uv run --no-sync pytest tests/mcp_tests -x -vv -n 4 --cov=./litellm --cov-report=xml --durations=5