Add workspace configure command

[codeforester]

Summary

• Add basectl workspace configure to apply the existing repo configure repair path across discovered workspace repos or a workspace manifest.
• Skip missing, non-Base-managed, or non-GitHub repos; continue after per-repo failures and report configured/skipped/failed counts.
• Update help, completions, docs, and .ai-context for the new workspace maintenance workflow.

Validation

• PYTHONPATH=lib/python:cli/python /Users/rameshhp/.base.d/base/.venv/bin/python -m pytest cli/python/base_projects/tests -q -> 101 passed, 4 subtests passed
• BASE_BASH_LIBS_DIR=/Users/rameshhp/work/base-bash-libs/lib/bash bats cli/bash/commands/basectl/tests/workspace.bats cli/bash/commands/basectl/tests/completions.bats cli/bash/commands/basectl/tests/repo.bats -> 92 passed
• PYTHONPATH=lib/python:cli/python /Users/rameshhp/.base.d/base/.venv/bin/python -m pylint --rcfile=.pylintrc cli/python/base_projects
• git diff --check
• env -u BASE_HOME BASE_BASH_LIBS_DIR=/Users/rameshhp/work/base-bash-libs/lib/bash ./bin/base-test -> Python 510 passed, 1 skipped; BATS 435 passed

Demo Impact

None. CLI workflow enhancement only.

Fixes #916