Sassy `mode` from config file is ignored (only CLI `--mode` works)

Start in shell_sage/core.py, comparing main() with get_opts() and tracing how mode is resolved from the config file. Verify that ssage with mode = sassy and no --mode uses the sassy persona, while explicit --mode behavior remains unchanged; also check the blank-mode edge case described in the issue.

When mode is set in the shell_sage config file (~/.config/shell_sage/shell_sage.conf), ShellSage still starts in default mode. The --mode sassy CLI flag works correctly, but the config value is never picked up.

Steps to reproduce

1. Set mode = sassy in ~/.config/shell_sage/shell_sage.conf
2. Run ssage "Say hello in one sentence" (no --mode flag)
3. Observe the response

Expected behavior

With mode = sassy in the config, ssage should respond in sassy mode (GLaDOS-style persona).

Actual behavior

ssage responds in the default teaching-assistant persona:

Hello! I'm ShellSage, your command-line teaching assistant — what shell task can I help you with today?

Running ssage --mode sassy "Say hello in one sentence" does produce the sassy persona, confirming the flag path works:

Hello, test subject — congratulations on successfully typing a query; I do hope that wasn't the most challenging part of your day.

Root cause

In shell_sage/core.py, main() never routes mode through get_opts(), which is where config-file values are resolved:

• main()'s mode parameter defaults to 'default' rather than None
• The get_opts(...) call does not pass mode=mode
• get_opts only fills a value from the config when the passed value is None (if v is None: opts[k] = cfg.get(k, default_cfg.get(k)))

So the config value for mode is never read.

Proposed fix (verified working locally)

1. Change the mode parameter default to None
2. Pass mode=mode to get_opts(...)
3. Use opts.mode for validation and the get_sage(...) call

Related edge case

If the config contains a blank mode = (e.g. from a generated config), opts.mode becomes '' and validation fails with is not valid. Must be one of: ['default', 'sassy']. Consider normalizing empty to default (opts.mode = opts.mode or 'default').

Environment

• Host: solveit (hosted notebook environment), Linux container
• Python 3.12
• shell-sage 1.0.9, installed editable from a git clone into an isolated venv (/app/data/aai-venv) — the system site-packages also has a stale shell-sage 1.0.9 which shadows the editable install for the default ssage binary
• Tested in a detached tmux session (via the fastmux pyskill) to give ssage a real TTY
• Config file: ~/.config/shell_sage/shell_sage.conf with mode = sassy, vendor_name = deepseek, model = deepseek-v4-flash

Dependency notes (may be relevant to maintainers)

• The repo's pyproject.toml requires python-fastllm>=0.0.38, but the system environment had fastllm 0.0.36 (no StreamAccum) — one reason testing was done in a venv
• The venv installed from local clones:
  • python-fastllm 0.0.41 (editable, from /app/data/git/fastllm)
  • fastcore 2.2.11 (editable, from /app/data/git/fastcore)
  • aidialog 0.0.19, fastspec 0.2.0 (satisfied via the fastllm install)
  • shell-sage 1.0.9 (editable, from /app/data/git/shell_sage)
• Because solveit itself imports fastcore/aidialog/fastllm, packages were deliberately not installed into the system environment — only into the isolated venv