Stop provisioning GitHub integration-test credentials in CI

[kylos101]

Description

Stop provisioning GitHub test-user credentials in CI so integration runs do not depend on that credential. Preserve the original tests, helpers, and manual commands; tests requiring credentials skip when they are absent.

Add the missing username guard to the disk test and retain the Go 1.25 formatting fixes. CI validation also exposed a process-limit assertion that inspected only stdout: inspect stderr too, where bash writes fork diagnostics, while retaining the required error check.

Related Issue(s)

None.

How to test

• Workspace suite: passed on 84cabdac3: 32 passed, 13 expected skips, zero failures; both maintenance checks passed separately. Confirmed all ten GitHub-context-dependent workspace entry points skipped. Cgroup and process-limit checks passed.
• Webapp suite: passed: server user lookup and builtin database user checks passed; two expected skips. The subsequent commit changes only the workspace process-limit assertion.
• Workspace validation used Branch Build with the existing on-demand preview option. Standalone attempts hit deployment/Spot-capacity problems; a reused-preview retry rejected its object-storage key. The successful run used a fresh preview after cleanup.
• All affected Go suites compile. Isolated credential-guard checks confirm 24 entry points skip without username/token, with no Git operations. Runner checks confirm explicit manual credentials are preserved and failures propagate.
• A bounded local process-limit reproduction confirmed the fork diagnostic is on stderr and the corrected assertion detects it.
• Formatting, golangci-lint for new issues, actionlint for the integration workflows, and pre-commit passed. IDE/default smoke workflows were not dispatched because their absent-credential paths provide no functional coverage.

Documentation

No public documentation changes required. Integration test documentation is updated.

Preview status

Disposable validation previews were removed. Final cleanup passed.

Build Options

Build

• /werft with-werft
  Run the build with werft instead of GHA
• leeway-no-cache
• /werft no-test
  Run Leeway with --dont-test

Publish

• /werft publish-to-npm
• /werft publish-to-jb-marketplace

Installer

• analytics=segment
• with-dedicated-emulation
• workspace-feature-flags
  Add desired feature flags to the end of the line above, space separated

Preview Environment / Integration Tests

• /werft with-local-preview
  If enabled this will build install/preview
• /werft with-preview
• /werft with-large-vm
• /werft with-gce-vm
  If enabled this will create the environment on GCE infra
• /werft preemptible
  Saves cost. Untick this only if you're really sure you need a non-preemtible machine.
• with-integration-tests=workspace
  Valid options are all, workspace, webapp, ide, jetbrains, vscode, ssh. If enabled, with-preview and with-large-vm will be enabled.
• with-monitoring

/hold

[kylos101]

Ditch the dependency on Github PAT