Use shared file section helpers in update-profile

[codeforester]

Summary

• Replace update_profile.sh's local marker-count and section-content temp-file comparison with shared base-bash-libs file section helpers.
• Add an import capability check for file_section_exists and file_section_needs_update so older helper checkouts fail clearly.
• Pin CI to base-bash-libs commit 424ef9fe61bc8a462ba9980ea63b38dd202ec242, which landed the companion helper PR.

Companion helper PR: basefoundry/base-bash-libs#124.

Fixes #1492.

Validation

• RED: env BASE_BASH_LIBS_DIR=/Users/rameshhp/work/base-bash-libs/lib/bash bats --filter "shared file section helper" cli/bash/commands/basectl/tests/update-profile.bats failed before implementation because the shared helper stubs were not called.
• PASS: env BASE_BASH_LIBS_DIR=/Users/rameshhp/work/base-bash-libs/lib/bash bats --filter "shared file section helper" cli/bash/commands/basectl/tests/update-profile.bats
• PASS: env BASE_BASH_LIBS_DIR=/Users/rameshhp/work/base-bash-libs/lib/bash bats cli/bash/commands/basectl/tests/update-profile.bats
• PASS: bash -n cli/bash/commands/basectl/subcommands/update_profile.sh cli/bash/commands/basectl/tests/update-profile.bats
• PASS: shellcheck -S warning cli/bash/commands/basectl/subcommands/update_profile.sh cli/bash/commands/basectl/tests/update-profile.bats
• PASS: env PYTHONPATH=lib/python:cli/python $HOME/.base.d/base/.venv/bin/python -m pytest tests/test_github_workflows.py
• PASS: git diff --check
• PASS: env -u BASE_HOME BASE_BASH_LIBS_DIR=/Users/rameshhp/work/base-bash-libs/lib/bash BASE_CACHE_DIR=/private/tmp/base-pr-train-1492 ./bin/base-test