Recurring 'token has no writable scopes' cache-save warning appears on every fullsend workflow run

What happened

Across all three agent runs traced for issue #131/PR #146 (triage run 35374932977, code run 35376105082, review run 35377373880, all in redhat-et/ProtoBot Actions), the workflow logs show a GitHub Actions cache-save step failing with a 'token has no writable scopes' warning. The job still completes successfully in each case — this is non-fatal — but it recurs on every single run in this trace, and a similarly-worded 'collaborator permission lookup failed for fullsend-ai-coder[bot]' notice appeared alongside it. During this retro's own log tracing, a subagent doing a naive grep -i error\|fail over the logs flagged both lines as apparent failures before determining they were benign, which cost extra investigation effort.

What could go better

I'm confident this warning recurs across runs (directly observed in three separate logs) and that it's currently non-blocking. I'm not certain whether the fix belongs in this repo's calling workflow file (its permissions: block, e.g. under .github/workflows/) or in the reusable fullsend workflow definition upstream (fullsend-ai/fullsend) — reusable workflows can only use permissions granted by the caller, so the caller's permissions block is the first place to check. Left unaddressed, this noise has a real (if modest) cost: it degrades the signal-to-noise ratio of log-based diagnosis for both humans and future retro/debugging agents, increasing the chance a genuine failure gets lost in known-benign noise or vice versa.

Proposed change

Investigate the permissions: block granted to the fullsend workflow jobs in this repo's .github/workflows/ calling file. If actions: write (or the specific scope the cache action needs) is missing there, add it. If the calling permissions are already sufficient and the gap is in how the reusable workflow itself requests/uses the cache action, file the fix against fullsend-ai/fullsend instead (the reusable workflow source) rather than here. Either way, the warning should stop appearing, or if a writable-scope grant is intentionally withheld for security reasons, the cache step should be made conditional/skippable so it doesn't log a failure-shaped warning on every run.

Validation criteria

The next 5 fullsend workflow runs (triage/code/review/fix) on this repo should show either no cache-save warning, or the cache step should be absent/skipped cleanly rather than logging a token-scope warning that greps for 'fail'/'error' would catch.

Generated by retro agent from https://github.com/redhat-et/ProtoBot/pull/146

Inspect the fullsend calling workflow under .github/workflows/ and its permissions block first, then compare the reusable workflow's cache usage in fullsend-ai/fullsend if caller permissions are sufficient. Trace the triage, code, review, and fix runs to identify the warning source. Done means five subsequent fullsend runs show no cache-save warning or skip the cache step cleanly.