Fix(ci): harden live launcher retries

[MohabMohie]

Summary

• Retry the shared live shaft-mcp launcher build after transient Maven Central failures, including failures in either Maven command.
• Preserve the final Maven exit status after all three attempts.
• Document the intentional bounded CI-only -am JUnit E2E build.
• Record the Bash -e retry constraint in project memory.

Companion documentation: ShaftHQ/shafthq.github.io#910 must merge before this PR so the pilot timeout documentation lands before #4365 closes.

Closes #4365
Closes #4373

Related to #4383

Test plan

• py -3 -m unittest tests/scripts/test_build_shaft_mcp_live_jar.py
• py -3 scripts/ci/validate_shaft_mcp_configuration.py
• py -3 scripts/agents/guard.py --self-test
• py -3 scripts/ci/validate_agent_setup.py --skip-external
• memory check

[codacy-production]

Not up to standards ⛔

🔴 Issues 2 medium · 1 minor

Alerts:
⚠ 2 issues (≤ 0 issues of at least medium severity)

Results:
3 new issues

Category	Results
Security	2 medium 1 minor

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🟢 Metrics 5 complexity · 2 duplication

Metric	Results
Complexity	5
Duplication	2

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