Offline mode

[kamocat]

• Adds support for existing "--offline" option
• Adds bundle-extract command to import a downloaded bundle (i.e. from circuitpython.org). Unfortunately, this breaks the dependency management. I am interested in ideas for how to fix this.

Offline Mode (--offline) Behaviour by Command

Command	--offline behaviour
install	Reads module list and resolves dependencies from local bundle only; no GitHub/PyPI calls. --stubs is silently skipped. Fails with "not a known library" if no bundle is extracted locally.
update	Compares device versions against local bundle; no GitHub calls. Post-update dependency check also uses local bundle. Will report everything as up-to-date if the local bundle tag is older than what's on the device.
list	Compares device versions against local bundle; no GitHub calls. Same caveat on stale local bundle.
freeze	Lists modules found on device with their installed versions; uses local bundle for version metadata. No network calls.
show	Always reads from local bundle only (no download regardless of --offline). No change in behaviour.
uninstall	No bundle or network access at all. No change in behaviour.
example	Always reads from local bundle only (avoid_download=True unconditionally). No change in behaviour.
bundle-show	Always reads from local bundle only. No change in behaviour.
bundle-add	Blocked — exits immediately with an error message when --offline is set.
bundle-remove	No network calls. No change in behaviour.
bundle-extract	No network calls (local zip only). No change in behaviour.
bundle-freeze	Reads from local bundle only (avoid_download=True unconditionally). No change in behaviour.

Notes applicable to all commands when --offline is set:

• The circup self-update check is skipped.
• The CircuitPython firmware latest-version check is skipped.
• If no bundle has been extracted locally, commands that need module metadata will fail or return empty results. Use circup bundle-extract <zip> first.
• Dependency resolution requires the py bundle to be extracted (the mpy zips do not include a requirements/ directory).