fix(browse): grant Windows ACLs to token SID, not bare username

[IntegriGit]

Problem

browse/src/file-permissions.ts hardens sensitive gstack state (auth/canary tokens, chat history, agent queue, device salt, per-tab security decisions) by breaking ACL inheritance and granting a single-entry ACL to the current user via icacls. It resolved that user with os.userInfo().username — the bare login name.

On a domain-joined Windows host that also has a local account of the same login name, icacls /grant lmiller:... resolves the bare name to the local SAM account (HOST\lmiller), not the domain account the process actually runs as (DOMAIN\lmiller). Combined with /inheritance:r, the new ACL is granted to an account the process is not, locking it out of the .gstack state directory it just created. The browse daemon then can't create its lock/state file and fails to start with a misleading:

Another instance is starting… Timed out.

This reproduced reliably on a domain-joined Windows 11 box (INTEGRIBILT\lmiller process vs. same-named local OFC01\lmiller).

Fix

Add currentUserIcaclsPrincipal():

• Resolves the current process token SID via System32\whoami.exe /user /fo csv /nh, called by absolute path so a shadowing Unix whoami earlier on PATH (e.g. Git-for-Windows) can't hijack it and force the weaker fallback.
• Grants icacls ... *S-1-5-… (SID literal), which is immune to local-vs-domain name collisions.
• Falls back to USERDOMAIN\username, then bare username, if the SID lookup is unavailable. Cached per process.

Both restrictFilePermissions and restrictDirectoryPermissions now use it instead of the bare os.userInfo().username. POSIX paths are unchanged.

Tests

bun test browse/test/file-permissions.test.ts — 15 pass / 0 fail.

Adds a regression test asserting the resolved principal is a SID literal (*S-1-5-…) on Windows, and a non-empty name-based fallback off-Windows. Verified on a domain-joined Windows 11 host: the emitted icacls grant is now *S-1-5-21-…:(F) rather than a bare name.

Co-Authored-By: Paperclip noreply@paperclip.ing

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