Make Milvus storage backend opt-in (storage-milvus group)

[howethomas]

Summary

pymilvus is the only consumer of pandas (~48MB) and grpcio (~37MB) in the project, yet neither is used directly anywhere in vcon-server. Milvus is just one of ~14 storage backends, and backends are loaded lazily via importlib.import_module only when a storage with that module is configured (common/storage/base.py). So pymilvus (and its heavy transitive deps) doesn't belong in the base install — this PR makes it opt-in.

Same theme as the transformers change (#188) and #160: a heavy, specialized dependency carried by every image despite shallow/optional use.

Changes

• pyproject.toml: move pymilvus>=2.3.0 out of the base storage group into a new opt-in storage-milvus group (which also includes openai, used by the backend for embeddings).
• test_milvus.py / test_milvus_branches.py: add pytest.importorskip("pymilvus") so both modules skip cleanly when the optional dep isn't installed (both import storage.milvus, which imports pymilvus at module load).
• docker/Dockerfile (dev/test image only): add --group storage-milvus so Milvus tests still run in CI. The production Dockerfile.conserver / Dockerfile.api images are untouched and now drop pymilvus/pandas/grpcio.
• Milvus README: document the opt-in install.
• uv.lock: regenerated — the pymilvus node is unchanged, just regrouped.

Impact

Removes ~85MB (pandas + grpcio) from the production conserver and api images for the common case that doesn't use Milvus.

⚠️ Breaking change

Deployments using the Milvus storage backend must now install it explicitly:

uv sync --group storage --group storage-milvus

Without it, loading storage.milvus raises a clear ImportError. (This is the intended opt-in behavior — every other storage backend already imports its own driver this way; this just stops bundling the heavy one by default.)

Testing

• common/storage/milvus/ (both test files): 25 passed with pymilvus present (tests run, not skipped — confirms importorskip doesn't break the running case).
• common/: 254 tests collect cleanly — no import errors from the regroup.
• uv lock --check passes (lock coherent with the regrouped manifest).

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR makes the Milvus storage backend an opt-in dependency by moving pymilvus (and its heavy transitive dependencies) out of the base storage dependency group into a new storage-milvus group, while keeping CI/dev images able to run the Milvus test suite.

Changes:

• Split Milvus dependencies into a new storage-milvus dependency group (pymilvus + openai) and updated the lockfile accordingly.
• Updated the dev/test Docker image to install storage-milvus so Milvus tests continue to run in CI.
• Made Milvus tests skip cleanly when pymilvus isn’t installed, and documented the opt-in install in the Milvus README.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
uv.lock	Removes pymilvus from base groups and adds a new storage-milvus group entry.
pyproject.toml	Moves pymilvus out of storage into a new optional storage-milvus group (includes openai).
docker/Dockerfile	Installs --group storage-milvus in the dev/test image so Milvus tests run in CI.
common/storage/milvus/test_milvus.py	Skips the Milvus test module when optional dependency isn’t present.
common/storage/milvus/test_milvus_branches.py	Same skip behavior for the branch coverage tests.
common/storage/milvus/README.md	Documents the opt-in installation for Milvus storage.

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 6 changed files in this pull request and generated 2 comments.

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