Add workspace onboarding summary

[codeforester]

Summary

• Add basectl workspace onboarding for a read-only first-day summary from a workspace manifest.
• Emit both text and JSON with expected paths, discovery status, next actions, clone guidance, and setup/check/test commands.
• Document the onboarding workflow and keep the Bash wrapper help/delegation in sync.

Validation

• /Users/rameshhp/.base.d/base/.venv/bin/python -m pytest cli/python/base_projects/tests/test_workspace_onboarding.py -q
• /Users/rameshhp/.base.d/base/.venv/bin/python -m pytest cli/python/base_projects/tests -q
• env BASE_BASH_LIBS_DIR=/Users/rameshhp/work/base-bash-libs/lib/bash bats cli/bash/commands/basectl/tests/workspace.bats
• bash -n cli/bash/commands/basectl/subcommands/workspace.sh
• /Users/rameshhp/.base.d/base/.venv/bin/python -m compileall -q cli/python/base_projects
• git diff --check

Fixes #1535