Packaging: sandbox extra breaks install on Windows, retrieval extra has no consumer #225

1. raven[sandbox] cannot be installed on Windows

pyproject.toml:

sandbox = [
    "boxlite==0.9.5",
    "anyio>=4.0",
]

boxlite publishes wheels for macOS and Linux only -- it is a microVM runtime built on KVM / Hypervisor.framework, and its PyPI classifiers say so explicitly (Operating System :: MacOS, Operating System :: POSIX :: Linux). That is by design upstream, not an oversight there.

The oversight is on our side: the dependency carries no platform marker, so on Windows the install fails outright:

error: Distribution `boxlite==0.9.5 @ registry+https://pypi.org/simple` can't be
installed because it doesn't have a source distribution or wheel for the current platform

This is purely a packaging defect, because the code already degrades gracefully when boxlite is absent:

• raven/sandbox/interfaces.py deliberately defines the shared types outside boxlite_executor.py so they "can be imported without requiring boxlite to be installed... they must not fail just because boxlite is absent".
• raven/cli/onboard_commands.py and raven/sandbox/debug_server.py probe with try: import boxlite / except ImportError.

So a Windows user who installs raven[sandbox] gets an install error instead of a Raven that simply reports the sandbox as unavailable.

Two sibling dependencies already do this correctly, which makes the omission clear:

"python-socks[asyncio]>=2.8.0,<3.0.0; sys_platform != 'win32'",
"matrix-nio>=0.25.2; sys_platform != 'win32'",

Fix: "boxlite==0.9.5; sys_platform != 'win32'".

2. The retrieval extra has no consumer

retrieval = [
    "torch>=2.0.0",
    "transformers>=4.45.0",
]

A whole-tree grep (excluding .venv, uv.lock, and node_modules) finds torch and transformers in exactly five places: this declaration, two code comments, one doc note, and a CI comment. Nothing imports either package -- not raven/, not tests/, not benchmarks/, scripts/, or demos/. There is no dynamic loading either (no sentence-transformers, AutoModel, from_pretrained, or string-based import), and no doc tells users to install raven[retrieval]. The extra dates back to the initial raven init commit, so it looks like scaffolding that never acquired a consumer.

It is not free to keep:

• torch is a multi-hundred-megabyte download that slows every environment build.
• Its native runtime is a known crash surface here. raven/cli/_exit.py documents that native runtimes loaded by the agent loop segfault Py_FinalizeEx, and the CLI hard-exits past finalization to dodge it; the test suite needed the same guard once CI started running the full suite.

Removing it changes no behaviour: the suite collects the same 4611 tests with and without it.

Proposed change

1. Add the sys_platform != 'win32' marker to boxlite.
2. Remove the retrieval extra (via uv remove, refreshing uv.lock).
3. Point CI back at --all-extras, which is now equivalent to today's hand-maintained channels + tools + sandbox list but stays correct as extras change.
4. Add windows-latest to the unit matrix, which the boxlite marker unblocks.

Step 4 is a measurement as much as a fix: the suite has never run on Windows, so it may surface platform assumptions. If it does, the marker fix still stands on its own and the matrix entry can wait.