ci(fro-bot): remove timeout and adjust checkout ref logic (#256)

* fix(ci): fix fro-bot checkout auth failure

The checkout step was failing with 'could not read Username' because
persist-credentials: false was added without restoring the ref parameter.
The ref parameter restricts fetches to a specific commit rather than
all refs, which works without full credential persistence.

Fixes Fro Bot CI check failure on this PR.

* ci(fro-bot): remove timeout and adjust checkout ref logic

* fix(ci): bypass checkout v6 includeIf.gitdir credential failure

Checkout v6's includeIf.gitdir credential mechanism intermittently
fails to authenticate during fetch (actions/checkout#2359, #2393).

Fix by setting the PAT as a global http.extraheader BEFORE checkout
runs, and disabling persist-credentials to prevent checkout from
using the broken includeIf.gitdir path. The global config survives
checkout's local-only credential cleanup.

* fix(ci): remove manual git credentials — handled by fro-bot agent

* fix(ci): restore global extraheader before checkout

* ci(fro-bot): drop configure git credentials step

---------

Co-authored-by: fro-bot <80104189+fro-bot@users.noreply.github.com>

Author: marcusrbrown

.github/workflows/fro-bot.yaml

@@ -103,7 +103,6 @@ jobs:
   fro-bot:
     name: Fro Bot
     runs-on: ubuntu-latest
-    timeout-minutes: 30
     if: >-
       (
         github.event.pull_request == null ||
@@ -175,3 +174,4 @@ jobs:
           model: ${{ vars.FRO_BOT_MODEL }}
           omo-providers: ${{ secrets.OMO_PROVIDERS }}
           prompt: ${{ env.PROMPT }}
+          timeout: 0