* Studio: make the startup public-IP lookup opt-in (#7307 P8)
Startup resolved the machine's external IP by asking ifconfig.me whenever
Studio bound to 0.0.0.0 or ::. That tells whoever runs that service this
host is running Unsloth, which the user never agreed to.
The lookup is now gated behind UNSLOTH_STUDIO_PUBLIC_IP_PROBE, off by
default, and logs plainly what it sends and where when enabled. Only
1/true/yes/on enable it, so a typo leaves the private default in place.
The other two steps stay unconditional because neither discloses
anything: the GCE metadata server is link-local, and the UDP connect only
asks the kernel which local address routes to 8.8.8.8 without putting a
packet on the wire. Disabling the probe therefore still yields a usable
LAN address for the access banner.
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* Studio: gate the check-host.net reachability probe too, and keep the cloud address
Problem 8 of #7307 is the check-host.net probe in _verify_global_reachability: it hands this machine's address and port to a third party and asks its nodes to connect back. That was still unconditional, so on GCE and on any host whose routing address is already public the reported behaviour was unchanged. It is now behind the same UNSLOTH_STUDIO_PUBLIC_IP_PROBE opt-in.
A private interface address is not proof the port is unreachable, since a NAT or cloud firewall can forward it. The private-address path no longer sets _public_reachable = False, so the banner keeps its warning instead of claiming local network only.
To stop the privacy default from costing cloud users their shareable address, step 1 now reads AWS IMDSv2 and Azure IMDS alongside GCE on link-local 169.254.169.254.
Also drops the redundant function-local import os and documents the variable in the README remote access section.
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* Studio: switch to a single UNSLOTH_STUDIO_DISABLE_PUBLIC_CHECK opt-out
Replaces the opt-in variable and the cloud metadata work from the previous commit. Both third-party startup lookups stay on by default, so nothing changes for existing users, and one variable turns both off for lab and privacy-sensitive deployments. That is the fallback the reporter offered in #7307 Problem 8, and it keeps the firewall diagnostic that the reachability check exists to provide.
The ifconfig.me lookup and the check-host.net probe are now both guarded by public_check_disabled(). Parsing matches the nearest existing switch, _trust_forwarded_for in utils/client_ip.py. The reachability guard sits after the private-address branch, which makes no network call, so a LAN user who opts out still gets the address note.
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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: danielhanchen <danielhanchen@gmail.com>
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