Prompt Dir Task Brief

Implement the tnh-gen --prompt-dir global flag.

Goal

Allow one-off tnh-gen calls to override the prompt catalog directory from the command line.

Example:

tnh-gen --prompt-dir ./test-prompts list

Expected Behavior

• Add a global --prompt-dir option to tnh-gen.
• The flag should override all lower-precedence prompt directory sources.
• The override should flow through the existing tnh-gen config loading path.
• Existing config behavior should remain unchanged when --prompt-dir is not supplied.

Precedence To Preserve

Effective precedence should be:

1. defaults and environment
2. user config
3. workspace config
4. explicit --config
5. CLI overrides, including --prompt-dir

Likely Files

• src/tnh_scholar/cli_tools/tnh_gen/tnh_gen.py
• src/tnh_scholar/cli_tools/tnh_gen/config_loader.py
• tests/cli_tools/test_tnh_gen.py
• tests/cli_tools/test_tnh_gen_coverage.py
• docs/cli-reference/tnh-gen.md

Validation

At minimum, run targeted tests covering:

poetry run pytest tests/cli_tools/test_tnh_gen.py tests/cli_tools/test_tnh_gen_coverage.py

If the implementation changes broader config behavior, add or run the relevant config tests too.

Success Criteria

• tnh-gen --prompt-dir <dir> list uses the supplied prompt directory.
• --prompt-dir wins over env, user config, workspace config, and explicit config file values.
• Missing or invalid prompt directory errors remain clear.
• CLI reference docs mention the new global flag.
• Targeted tests pass.