Add workspace manifest reporting

[codeforester]

Summary

• Add local workspace manifest parsing and validation for schema_version, workspace.name, and repos.
• Add read-only --manifest support to basectl workspace status/check/doctor, including required/optional missing repos and outside-manifest local projects.
• Document BASE-W workspace finding IDs, JSON fields, shell help, and completions.

Validation

• env -u BASE_HOME PYTHONPATH=/Users/rameshhp/work/base-worktrees/feature-511-workspace-manifests/lib/python:/Users/rameshhp/work/base-worktrees/feature-511-workspace-manifests/cli/python /Users/rameshhp/.base.d/base/.venv/bin/python -m pytest cli/python/base_projects/tests/test_workspace_manifest.py cli/python/base_projects/tests/test_workspace_status_manifest.py cli/python/base_projects/tests/test_engine.py cli/python/base_projects/tests/test_workspace_checks.py -q
• env -u BASE_HOME PYTHONPATH=/Users/rameshhp/work/base-worktrees/feature-511-workspace-manifests/lib/python:/Users/rameshhp/work/base-worktrees/feature-511-workspace-manifests/cli/python /Users/rameshhp/.base.d/base/.venv/bin/python -m pylint --rcfile=.pylintrc cli/python/base_projects/engine.py cli/python/base_projects/workspace_manifest.py cli/python/base_projects/workspace_reports.py cli/python/base_projects/tests/test_engine.py cli/python/base_projects/tests/test_workspace_checks.py cli/python/base_projects/tests/test_workspace_manifest.py cli/python/base_projects/tests/test_workspace_status_manifest.py
• env -u BASE_HOME bats cli/bash/commands/basectl/tests/workspace.bats cli/bash/commands/basectl/tests/completions.bats
• shellcheck -S error cli/bash/commands/basectl/subcommands/workspace.sh lib/shell/completions/basectl_completion.sh
• zsh -n lib/shell/completions/basectl_completion.zsh
• git diff --check
• git diff --cached --check
• env -u BASE_HOME ./bin/base-test

Demo Impact

• Adds read-only workspace reporting for expected repository sets. No mutating clone/pull/reset behavior.

Closes #511