Add manifest command trust commands

[codeforester]

Summary

• Add base_trust with manifest command trust identity computation, local allow-record storage, JSON status output, allow, and revoke.
• Add basectl trust status|allow|revoke Bash dispatch plus Bash/Zsh completions.
• Document the trust command surface in command references, AI command context, and the changelog.

Fixes #1381

Validation

• env PYTHONPATH=/Users/rameshhp/work/base-worktrees/1381-manifest-command-trust/lib/python:/Users/rameshhp/work/base-worktrees/1381-manifest-command-trust/cli/python /Users/rameshhp/.base.d/base/.venv/bin/python -m pytest cli/python/base_trust/tests/test_engine.py lib/python/base_cli/tests/test_public_command_lifecycle.py -q
• env PYTHONPATH=/Users/rameshhp/work/base-worktrees/1381-manifest-command-trust/lib/python:/Users/rameshhp/work/base-worktrees/1381-manifest-command-trust/cli/python /Users/rameshhp/.base.d/base/.venv/bin/python -m pylint --rcfile=.pylintrc cli/python/base_trust
• env -u BASE_HOME BASE_BASH_LIBS_DIR=/opt/homebrew/opt/base-bash-libs/libexec/lib/bash bats cli/bash/commands/basectl/tests/help.bats
• env -u BASE_HOME HOME=/private/tmp/base-trust-smoke-1381-home BASE_PROJECT_VENV_DIR=/Users/rameshhp/.base.d/base/.venv BASE_BASH_LIBS_DIR=/Users/rameshhp/work/base-bash-libs/lib/bash ./bin/basectl trust allow base --manifest-sha256 f0d990bd80d63e5afeec78759a20b4686c4995872536a83ac9345f417cde7c41
• env -u BASE_HOME BASE_BASH_LIBS_DIR=/opt/homebrew/opt/base-bash-libs/libexec/lib/bash ./bin/base-test