Prevent background Cursor login browser launches

[yaacovcorcos]

Summary

• prevent Scient's background Cursor health, model-discovery, and ACP subprocesses from opening an authentication browser
• use Cursor Agent's documented NO_OPEN_BROWSER variable while retaining the existing generic browserless guards
• preserve the explicit user-triggered Connect flow unchanged

Root cause

Scient already attempted to make background Cursor processes browserless with NO_BROWSER=true, but Cursor Agent 2026.07.23-e383d2b checks the distinct NO_OPEN_BROWSER variable before launching its authentication page. An unauthenticated background models call could therefore open a browser unexpectedly.

Verification

• focused provider/Cursor suites: 206 passed
• bun run fmt:check
• bun run lint (0 errors; existing warnings only)
• bun run typecheck (9/9)
• bun run test (12/12 tasks; CLI/server 2,330 passed and 9 skipped)
• bun run build:desktop (5/5 tasks)
• git diff --check
• installed Cursor Agent manual check: with NO_OPEN_BROWSER=1, unauthenticated status and models returned without opening a browser

Scope and risk

The new flag is applied only through the shared environment for background/probe/ACP Cursor subprocesses. The explicit cursor-agent login command launched after a user clicks Connect does not use this environment and remains able to open authentication normally.

No UI or visual changes. No migration, persistence, credential, permission, packaging, updater, or release-control changes.

Overlap

Open PR #68 changes the broader provider connection UI and tests, but does not modify the shared Cursor browserless environment or the files changed here.

Rollback

Revert this PR to restore the previous environment. No stored state or migration rollback is required.

[yaacovcorcos]

Parent planning documentation: Scient PR https://github.com/ScientFactory/Scient/pull/48. The Cursor item is intentionally absent from the open inbox because this PR implements it.