test(bind): cover bounded shutdown recovery

[bryanwieg]

Summary

• add canonical process-level coverage for bounded RNDC, SIGTERM, and SIGKILL recovery
• verify PID replacement is never signaled and watcher handling remains safe
• protect BIND General Log routing/default severity
• keep the suite compatible with 26.1 and pre-feature 26.7 sources through an explicit release threshold
• materialize trusted master-owned CI helpers and canonical tests for release-branch PRs

Verification

• 26.1 source: 144 passed, 7 expected skips, 5 subtests passed
• current 26.7 source: 144 passed, 7 expected skips, 5 subtests passed
• fixed 26.7 source: 151 passed, 5 subtests passed
• CI helper suite: 295 passed, 3 subtests passed
• independent standards, simplification, and test-suite reviews: pass

This canonical-test/control-plane PR must merge before #95 so the release workflow exercises the new behavior.