fix(rule): prevent concurrent double start

[ngjaying]

Summary

• Prevent a stale rule start operation from launching a topology after another start path has already completed.
• Cover both normal and scheduled start paths with a deterministic concurrency regression test.
• Refresh the modified files' copyright years to 2026.

Why

• RestartRule eventually calls State.Start, while a concurrent StartRule calls State.Bootstrap.
• Start changed the state to Starting before acquiring ruleLock. If Bootstrap acquired the lock and completed first, the waiting Start continued without checking the new state and launched a second runTopo goroutine for the same topology.
• This is a logical race rather than an unsynchronized memory access, so the Go race detector does not report it.

Changes In This PR

• Recheck that the rule is still in Starting state after Start or ScheduleStart acquires ruleLock.
• Return without planning or launching when another lifecycle operation has already advanced the state.
• Add a deterministic test that holds ruleLock, lets the start path enter Starting, models Bootstrap completing first, and verifies the stale start performs no topology work.

Notes

• The change only affects concurrent lifecycle operations on the same rule.
• Sequential start, restart, stop, recovery, and scheduled-rule behavior are unchanged.
• Validated with:
  • go test -race ./internal/topo/rule/... -count=1
  • focused regression test under -race for 10 consecutive runs
  • focused REST rule-management tests under -race
  • go vet ./internal/topo/rule/...
  • git diff --check

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.75%. Comparing base (3cc4206) to head (f6f25de).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4076      +/-   ##
==========================================
- Coverage   70.76%   70.75%   -0.01%     
==========================================
  Files         462      462              
  Lines       54269    54275       +6     
==========================================
+ Hits        38400    38401       +1     
- Misses      12883    12887       +4     
- Partials     2986     2987       +1     

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