fix(mongodb): bound switchover completion

[weicao]

Problem

MongoDB switchover currently treats any non-primary role as success, invokes
syncer without a response deadline, and returns immediately after the request.
The syncer request only creates a completion ConfigMap; actual promotion is
complete when MongoDB HA deletes that token. A connected syncer that withholds
its response can also block indefinitely.

Change

• validate exact primary/secondary roles and required identities;
• submit exactly one syncer request under a 10-second bound;
• observe exact completion-token deletion through six bounded kubectl probes;
• preserve request/probe failures and timeout statuses without replay;
• keep the script POSIX for every resolved MongoDB action image;
• render all three switchover actions with the projected kubectl path,
  visible classified stderr, and a 50-second action ceiling; and
• add a contract suite covering roles, candidates, failures, completion,
  all supported ComponentVersion image mappings, and tool producers.

Evidence

• focused ShellSpec: Bash 3.2 24/0, Bash 5.3 24/0;
• full MongoDB ShellSpec: Bash 3.2 102/0, Bash 5.3 102/0;
• actual resolved 8.0.17 image: hanging request, hanging probe, and absent
  candidate rows pass;
• Helm lint and default/custom-data-path renders pass;
• POSIX sh -n, ShellCheck warning, diff-check, strict fsck, and clean
  worktree pass;
• fresh independent design review: DESIGN_CLEAR / BLOCKER_LIST0;
• fresh independent implementation review: APPROVE / BLOCKER_LIST0.

Boundaries

This PR contains static and container-local evidence only. It does not claim
Kubernetes runtime acceptance, package readiness, formal product N, merge,
deploy, or release readiness.

Open PR #3241 and PR #3110 remove the current kubectl producer from the same
ComponentDefinitions. Any future rebase must preserve both kubectl on the
selected data volume and syncerctl on /tools.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 244 lines in your changes missing coverage. Please review.
✅ Project coverage is 0.00%. Comparing base (8e745a4) to head (9824ce8).

Files with missing lines	Patch %	Lines
...ongodb/scripts-ut-spec/switchover_contract_spec.sh	0.00%	244 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff           @@
##            main   #3278    +/-   ##
======================================
  Coverage   0.00%   0.00%            
======================================
  Files        165     166     +1     
  Lines      25632   25876   +244     
======================================
- Misses     25632   25876   +244     

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