v1.91.4.0 fix: Windows Opera cookie import wave (#2980, refs #2957) (#2987)

* fix: support Windows Opera and Opera GX cookie imports

Fixes #2957

* fix: repair Windows cookie decryption and make Opera import failures actionable

- strip the SHA-256(host_key) prefix Chromium adds to v10 values (DB meta v24+) on Windows
- keep receipts and name `$B handoff` recovery for App-Bound rows in browsers without native extraction
- explain missing browsers, missing profiles and ambiguous profile selection with next steps
- add windowsNative/resolveBrowserInfo, the operagx alias and sorted failure reasons in CLI output
- cover the Node server runtime with a real-DPAPI Windows test

* docs: document Windows Opera cookie import and guard browser lists against drift

* chore: file cookie-import follow-ups from the Opera fix wave review

* test: keep Opera receipt tests independent of the shared key cache

* test: declare generated gstack/llms.txt as a command-reference input for PR selection

* chore: release v1.91.4.0

* test: reconstruct the historical cookie-workflow approval after the Opera BROWSER.md additions

* test: run the real-DPAPI Windows check with the runner's environment

PowerShell launched with a stripped environment took ~18-21s on the Windows
runner (measured on a throwaway diagnostics run), past dpapiDecrypt's 10s
deadline; with the full environment it returns in ~0.3s. Only APPDATA is
redirected to the fixture's Opera root.

---------

Co-authored-by: Matt Van Horn <455140+mvanhorn@users.noreply.github.com>

agents-digest/gstack-AGENTS.md

@@ -1,4 +1,4 @@
-# gstack digest v1.91.2.0 — regenerate/re-copy after upgrading gstack
+# gstack digest v1.91.4.0 — regenerate/re-copy after upgrading gstack
 
 Behavioral rules from gstack (https://github.com/garrytan/gstack), compressed
 for agent hosts without a full skill install. The full skills add workflows,