fix(mongodb): align example service versions

[weicao]

What this fixes

MongoDB example and README serviceVersion references had drifted from the releases supported by the rendered replica ComponentVersion:

4.0.28, 4.4.29, 5.0.29, 6.0.27, 7.0.28, 8.0.17

The stale surfaces included unsupported restore 6.0.16, unsupported selected snippet 7.0.1, incomplete cluster option comments, and stale version tables.

Changes

• align both MongoDB README version tables and selected-version snippets
• align canonical cluster and restore YAML examples
• align chart README embedded copies with the canonical YAML
• add a structural ShellSpec that derives the supported set from rendered ComponentDefinition/ComponentVersion data
• make the focused check fail closed on dependency/render infrastructure failures before parsing output

Verification

• focused ShellSpec: Bash 3.2 4/0; Bash 5.3 4/0
• full MongoDB ShellSpec: Bash 3.2 22/0; Bash 5.3 22/0 with the pre-existing dataprotection regex warning
• independent structural oracle: 79/0 in both shells; eight source mutants RED
• dependency/render fail-closed probes: exact helper rc 2; source drift rc 1; aligned candidate rc 0
• Helm dependency build, lint, template, and 28-document YAML parse pass
• dual-shell syntax, ShellCheck error severity, and git diff --check pass

Boundary

This is source/static reference closure only. It does not establish package, deployment, runtime, minimum-version acceptance, or release readiness.

Closes #3261

[leon-ape]

LGTM