fix(nous): force PYTHONUNBUFFERED=1 so device-code output surfaces

The sign-in sheet was stuck on the "Contacting Nous Portal…" spinner
even though hermes was running correctly. Root cause: Python
block-buffers stdout when it's a pipe instead of a TTY, and
`hermes auth add nous` enters a 15-minute polling loop after printing
the device-code block without ever calling `input()` — so nothing
flushes the buffer. Our readability handler never receives the URL +
user_code lines.

PKCE doesn't hit this because hermes calls `input("Authorization
code: ")`, which flushes stdout before blocking. Device-code has no
equivalent trigger.

Setting PYTHONUNBUFFERED=1 in the subprocess environment forces
line-buffered stdout for the duration of the flow — the device-code
block surfaces immediately, our regex extracts the URL and code, and
the sheet transitions into the waitingForApproval state as intended.

Local-only fix; remote SSH contexts get the remote's login env
untouched (the user's remote shell config owns buffering behavior
there).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scarf/scarf/Core/Services/NousAuthFlow.swift

@@ -68,7 +68,22 @@ final class NousAuthFlow {
         if !context.isRemote {
             // Only enrich env locally — remote ssh gets the remote login env
             // naturally, and exporting our local keys into it would be wrong.
-            proc.environment = HermesFileService.enrichedEnvironment()
+            var env = HermesFileService.enrichedEnvironment()
+            // Python block-buffers stdout when it's a pipe (not a TTY). The
+            // device-code flow prints the verification URL + user code, then
+            // enters a ~15-minute polling loop that never hits `input()` —
+            // so nothing flushes and our readability handler never sees the
+            // output. Users see the sheet spinning forever while hermes is
+            // actually waiting for approval.
+            //
+            // PKCE doesn't have this problem because `input("Authorization
+            // code: ")` flushes stdout before blocking, which is why
+            // OAuthFlowController works without this setting.
+            //
+            // PYTHONUNBUFFERED forces line-buffered stdout for the whole
+            // subprocess — tiny perf cost, huge UX win for device-code.
+            env["PYTHONUNBUFFERED"] = "1"
+            proc.environment = env
         }
 
         let outPipe = Pipe()