Add a no-worktree workspace mode

[nbashaw]

Summary

• add a --no-worktree path to the top-level trycycle skill so it can reuse the current checkout or a Conductor workspace instead of always creating a nested git worktree
• update prompt templates, docs, and explorer samples to describe the implementation workspace consistently in both modes
• make the finishing flow workspace-aware and make maintenance/import-skills.sh portable on macOS Bash 3.2

Verification

• bash -n maintenance/import-skills.sh
• rendered prompt templates successfully with /opt/homebrew/bin/python3.13 orchestrator/prompt_builder/build.py

Notes

• bash maintenance/import-skills.sh is still blocked by an expired Claude OAuth token (401 authentication_error), so I manually synchronized the generated planning/finishing subskills in this branch after updating the maintenance inputs
• the existing repo test file was not runnable here: pytest is not installed in the available interpreters, and python3.13 -m unittest discover -s tests -v fails because tests/test_validate_rendered_prompt.py hardcodes /home/user/code/trycycle