refactor: simplify and harden code since v2.1.0 release

[itdove]

Jira Issue:

Description

Simplification and hardening of code changes since the v2.1.0 release, based on automated /simplify and /code-review analysis.

Simplification (7 items):

• Extract strip_code_fences() utility, replacing 6 duplicate instances across complete_command.py and pr_template.py
• Deduplicate temp directory cleanup in open_command.py by delegating to canonical cleanup_temp_directory() from temp_directory.py
• Deduplicate PR template AI prompt (built once, passed to API fallback) and pass pre-loaded config to _fill_template_fallback
• Cache package_file_name property in ReleaseManager, replacing 2 inline expressions that re-read pyproject.toml
• Extract _clone_repo_to_temp() shared core from clone_to_temp_directory and prompt_and_clone_to_temp
• Fix duplicate git ls-remote call in open_command.py (wasted network round-trip)

Code review fixes (6 items):

• Fix _cleanup_temp_directory in complete_command.py not handling nested daf-session-* directories (orphaned temp dirs)
• Fix unbound prompt variable in pr_template.py FileNotFoundError handler
• Sanitize issue_key in investigate_command.py session name to prevent path separators
• Use lambda in re.sub for session.goal to prevent regex backreference interpretation
• Tighten JIRA placeholder regex from \w+ to \d+ to avoid matching words like ISSUE-HANDLING
• Add Path.resolve() to temp directory cleanup for macOS symlink compatibility

Assisted-by: Claude

Testing

Steps to test

1. Pull down the PR and run python -m pytest tests/ -x -q
2. Verify 3609+ tests pass (1 pre-existing flaky test in test_workspace.py is unrelated)
3. Run daf investigate #123 or daf investigate owner/repo#123 and verify session name is sanitized
4. Run daf complete on a ticket_creation session and verify temp directory cleanup removes the parent daf-session-* directory

Scenarios tested

• Full test suite: 3609 passed, 65 skipped, 1 pre-existing flaky
• PR template tests: 23 passed (updated for new function signatures)
• Temp directory tests: 57 passed
• Investigate command tests: 22 passed
• Release manager tests: 49 passed

Deployment considerations

• This code change is ready for deployment on its own

🤖 Generated with Claude Code