feat(fish): complete Fish shell adapter with full feature parity

[lacymorrow]

Summary

Closes #36. Completes the Fish shell adapter (Fish 3.1+) with full feature parity against the Bash adapter:

• Detection: Full _lacy_classify_input with all ~150 agent words, shell reserved words, @/! bypass prefixes, env-var assignment handling, and multi-word heuristics
• Execution routing: Enter key intercepts, session commands (/new, /reset, /clear, /resume), emergency/agent bypass prefixes
• User commands: mode, tool, ask, quit/stop — all available as Fish functions
• Tool support: All 10 AI tools (lash, claude, opencode, gemini, codex, hermes, copilot, goose, amp, aider) + custom
• Tab completions: For lacy, mode, and tool commands
• Keybindings: Enter override via bind \r, Ctrl+Space mode toggle, coexists with user's fish_user_key_bindings
• Prompt: Mode badge in fish_right_prompt (wraps existing right prompt if present)
• Cleanup/quit: Full teardown restoring original bindings and prompt

Also updates bin/lacy completions fish, README, CLAUDE.md, and docs to reflect Fish support.

Test plan

• Install Fish 3.1+ and source lacy.plugin.fish
• Verify mode toggle (Ctrl+Space cycles auto → shell → agent → auto)
• Verify detection: ls -la → shell, what files are here → agent
• Verify /new and /resume session commands
• Verify !cmd bypass sends directly to shell
• Verify @query bypass sends directly to agent
• Verify mode shell, mode agent, mode auto commands
• Verify tool shows installed tools, tool set claude switches
• Verify ask "question" routes to agent
• Verify quit cleans up bindings and restores prompt
• Verify lacy completions fish outputs valid completions script

[gemini-code-assist]

Code Review

This pull request adds support for the Fish shell (3.1+) by implementing a native adapter for natural language detection, execution routing, and keybindings. The update includes new Fish-specific library files, documentation updates, and expanded CLI completions. Feedback identifies critical bugs in the cleanup routine, specifically that Enter keybindings and original user functions are not restored, which could break the shell. Other improvements suggested include refining the input classification heuristic to handle multiple spaces and ensuring the "ask" command supports multi-word queries.

[gemini-code-assist]

Erasing the \n and \r bindings without restoring them will leave the shell unusable (the Enter key will stop working) until the shell is restarted. Instead of erasing, you should restore the default execute binding.

    bind \n execute 2>/dev/null
    bind \r execute 2>/dev/null

[gemini-code-assist]

The fish_user_key_bindings function was wrapped in lib/fish/keybindings.fish but is not restored during cleanup. This leaves a broken function that attempts to call the erased _lacy_setup_bindings function. You should restore the original function if it was backed up.

    # Restore original keybindings function if we wrapped it
    if functions -q _lacy_original_key_bindings
        functions -c _lacy_original_key_bindings fish_user_key_bindings
        functions --erase _lacy_original_key_bindings
    end

    # Remove user-facing command functions
    functions --erase mode tool ask quit stop 2>/dev/null

[gemini-code-assist]

Using string split ' ' will include empty strings in the result if the input contains multiple consecutive spaces (e.g., ls -la). This can cause the word_count and the bare word heuristic (lines 105-112) to behave incorrectly, potentially routing valid shell commands to the agent. Use the -n (or --no-empty) flag to skip empty results.

    set -l words (string split -n ' ' -- "$input")

[gemini-code-assist]

The ask function currently only sends the first word of the query to the AI agent because _lacy_query_agent only processes $argv[1]. To support multi-word queries without requiring quotes, join the arguments into a single string.

    _lacy_query_agent (string join ' ' -- $argv)