Add `undetermined-cipher-scenario-logic` feature flag (#7802)

Introduced in Browser 2026.2.0 via bitwarden/clients#18395. Rewrites the
post-submit add/update login notification triggering logic, deferring
cipher-type inference until the vault is unlocked. Client-side only.

.env.template

@@ -409,6 +409,7 @@
 ## - "desktop-ui-migration-milestone-3": Special feature flag for desktop UI (Desktop >= 2026.2.0)
 ## - "desktop-ui-migration-milestone-4": Special feature flag for desktop UI (Desktop >= 2026.2.0)
 ## - "enable-basic-auth-response": Enable HTTP Basic Auth autofill in the browser extension (Browser >= 2026.9.0)
+## - "undetermined-cipher-scenario-logic": Enable the rewritten add/update login notification triggering logic in the browser extension (Browser >= 2026.2.0)
 # EXPERIMENTAL_CLIENT_FEATURE_FLAGS=
 
 ## Require new device emails. When a user logs in an email is required to be sent.

src/config.rs

@@ -1427,6 +1427,7 @@ pub const SUPPORTED_FEATURE_FLAGS: &[&str] = &[
     "pm-5594-safari-account-switching",
     "pm-32413-multi-client-password-management",
     // Autofill Team
+    "undetermined-cipher-scenario-logic",
     "enable-basic-auth-response",
     "ssh-agent",
     "ssh-agent-v2",