fix(mariadb): fail closed on unsafe Galera bootstrap

[weicao]

Summary

• stop pod-0 from rewriting safe_to_bootstrap: 0 to safe_to_bootstrap: 1 during full Galera crash recovery
• log the local wsrep-recover seqno as evidence only
• fail closed when no peers are alive and the latest node cannot be proven locally
• add focused shellspec coverage for unsafe and already-safe pod-0 bootstrap paths

Closes #2996.

Validation

• shellspec --load-path ./shellspec --shell bash addons/mariadb/scripts-ut-spec/galera_start_spec.sh -> 7 examples, 0 failures
• bash -n addons/mariadb/scripts/galera-start.sh addons/mariadb/scripts-ut-spec/galera_start_spec.sh
• git diff --check -- addons/mariadb/scripts/galera-start.sh addons/mariadb/scripts-ut-spec/galera_start_spec.sh

Evidence boundary

This PR fixes the source-level unsafe bootstrap path and has focused unit coverage. It does not claim that the full Galera crash-recovery scenario is runtime-passed until the patched chart/image is validated in a live cluster.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 52 lines in your changes missing coverage. Please review.
✅ Project coverage is 0.00%. Comparing base (931738c) to head (4acd3fa).

Files with missing lines	Patch %	Lines
...ddons/mariadb/scripts-ut-spec/galera_start_spec.sh	0.00%	49 Missing ⚠️
...ts-ut-spec/seed_replication_mode_overrides_spec.sh	0.00%	3 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #2997   +/-   ##
=====================================
  Coverage   0.00%   0.00%           
=====================================
  Files        140     140           
  Lines      22548   22597   +49     
=====================================
- Misses     22548   22597   +49     

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[leon-ape]

With the new pod-0 fail-closed path, the existing non-pod-0 guard still ignores safe_to_bootstrap: 1. In a clean full shutdown where Galera marks a non-pod-0 as the safe node, pod-0 exits with the defer reason and that safe non-pod-0 also returns false to join, so no pod bootstraps the cluster.

[weicao]

Addressed in cdb834aec9d68b981a210b4a902356540ce14c87.

Change made:

• a node with local safe_to_bootstrap: 1 can bootstrap after the no-Primary-peer check, regardless of pod index
• safe_to_bootstrap: 0 still stays fail-closed on pod-0 and no longer rewrites grastate.dat
• added shellspec coverage for the clean full-shutdown case where Galera marks a non-pod-0 as safe

Local validation on the rebased commit:

• shellspec --load-path ./shellspec --shell bash addons/mariadb/scripts-ut-spec/galera_start_spec.sh -> 8 examples, 0 failures
• bash -n addons/mariadb/scripts/galera-start.sh addons/mariadb/scripts-ut-spec/galera_start_spec.sh
• git diff --check -- origin/main..HEAD

[weicao]

Addressed fresh Galera bootstrap regression in 3a4ae56a85ed10ddea4fe9dae13891b11c6cc224.

Change made:

• treat grastate.dat with seqno=-1 as fresh bootstrap state, not a clean-shutdown election result
• keep fresh bootstrap single-owner on pod-0 to prevent pod-0/1/2 from each forming their own Primary component
• preserve the previous clean full-shutdown behavior: a non-pod-0 node with safe_to_bootstrap: 1 and a real seqno can still bootstrap after the no-Primary-peer check
• keep pod-0 with safe_to_bootstrap: 0 fail-closed and non-mutating

Local validation:

• shellspec --load-path ./shellspec --shell bash addons/mariadb/scripts-ut-spec/galera_start_spec.sh -> 10 examples, 0 failures
• bash -n addons/mariadb/scripts/galera-start.sh addons/mariadb/scripts-ut-spec/galera_start_spec.sh
• git diff --check -- origin/main..HEAD

[leon-ape]

LGTM