fix(repo-assist): remove title-prefix restriction from push-to-pull-request-branch

[yskopets]

Problem

The repo-assist workflow has title-prefix: "[Repo Assist] " set on its push-to-pull-request-branch safe output:

safe-outputs:
  push-to-pull-request-branch:
    target: "*"
    title-prefix: "[Repo Assist] "
    max: 4

This configuration is self-contradictory. target: "*" says "push to any PR", but title-prefix: "[Repo Assist] " rejects every push to a PR whose title doesn't start with [Repo Assist] — which is every PR not originally created by Repo Assist.

Impact

When a user invokes /repo-assist to fix CI failures, address review comments, or update an open PR created by a human or another workflow, the agent correctly identifies the changes needed, generates the patch, and queues a push_to_pull_request_branch operation. The safe_outputs job then silently rejects it with:

✗ Message 1 (push_to_pull_request_branch) failed: Pull request title "[other-workflow] ..."
  does not start with required prefix "[Repo Assist] "

The user gets no useful feedback, and the fix is never applied.

Root Cause

title-prefix on push-to-pull-request-branch was likely copied from create-pull-request where it makes sense (to namespace PRs Repo Assist creates). On push-to-pull-request-branch it has the opposite effect — it prevents Repo Assist from pushing to PRs it didn't create, which is precisely the on-demand use case.

Fix

Remove title-prefix from push-to-pull-request-branch in workflows/repo-assist.md:

safe-outputs:
  push-to-pull-request-branch:
    target: "*"
    max: 4

title-prefix should remain on create-pull-request where it namespaces new PRs correctly. The max: 4 cap and existing protected-files guardrails already provide the right safety boundary for pushes.

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Issue filed by Claude (Anthropic)

[dsyme]

@yskopets One problem with this is that it means repo-assist can choose to update PRs from other users. We could prompt against that, but it does remove a guardrail that exists today.

For this reason we currently prefer people to make this change locally if they deem it approproate - edit your local workflow.