feat(keys): configurable vim-style keybindings

[Rfluid]

Summary

Adds keyboard shortcuts to the modal: vim-style defaults, a user override file (~/.config/aura/keybindings.toml) with warnings for bad entries, a master switch in config.toml, and an aura keys CLI that mirrors aura config.

Keymap

• Defaults:

  Keys	Does
  j/k, ctrl-d/ctrl-u, ctrl-f/ctrl-b, g g/G	Scroll
  h/l, tab, g t/g T, 1–9	Section tabs
  H/L, [/]	Previous / next agent or plugin
  m	Switch agents ↔ plugins
  p/P	Cycle the period
  r	Refresh
  ,	Settings
  .	More menu
  ?	Help
  q	Close the window
  esc	Close the open overlay (then the window)

• Contexts: [global] applies everywhere. [overlay] applies while a menu, the settings panel or the help is open, and wins over [global] for the same keys.

• Overrides: "none" unbinds a key. use_defaults = false starts from an empty keymap.

• Loading never fails. A bad entry is skipped with a warning; the rest still applies. Aura warns about:

  • invalid TOML (the whole file falls back to the defaults)
  • unknown tables or actions, with a "did you mean"
  • bad keystrokes, and values that aren't strings
  • the same key written two ways (G / shift-g)
  • unbinding a key that has no binding
  • a key that starts a longer sequence (g alongside g g)
  • taking over the text-selection keys (ctrl-c, ctrl-a, shift+arrows)

• Where warnings show up: a header chip with the count, the top of the ? help overlay, stderr (once per distinct set), aura keys validate (exits 1), and aura doctor.

• Off switch: [keybindings] enabled = false in config.toml turns every shortcut off. Escape still closes the window.

• Reloading: the keymap is re-read on every open and every refresh, with no restart needed.

CLI: aura keys (alias aura keybindings)

Command	Does
path	Print the file path
list [--context]	Effective keymap, where each binding came from, and warnings
describe [action|keys]	List every action, or explain one action or keystroke
get <keys>	What a keystroke does
set <keys> <action> / unbind <keys>	Bind or unbind a keystroke
reset <keys>, --action, --all	Drop overrides so the defaults apply again
wizard	Step through every action interactively
merge <file|->	Merge another keymap in; --prefer theirs|ours, --check
export	Print the full effective keymap as a standalone file
init [--full]	Write a starter file
document	Rewrite the file with a description on every entry
validate	Report problems; exit 1 if any
edit	Open the file in $EDITOR

Read commands take --format json. The write commands go through KeymapFile, which edits with toml_edit, so they keep the user's comments and layout.

Implementation notes

• aura-core/src/keymap/ holds the parser, defaults, merge logic and warnings (mod.rs) and the file editor (file.rs). Neither has any UI code; the CLI and the modal share them.
• aura/src/keys.rs defines one GPUI action per KeyAction, wired through an exhaustive match so an unwired action won't compile.
• Focus: the modal root now holds a FocusHandle, because GPUI dispatches bindings only from a focused element. This reverses the "no focus handles" note in docs/plans/selectable-text.md. Nothing else in the modal is focusable, and a click anywhere puts focus back on the root.
• Binding order: [global] and [overlay] are key contexts on the same root element, so GPUI can't rank them by depth and falls back to insertion order. Overlay bindings are therefore installed last.
• Other changes:
  • New toml_edit dependency in aura-core. It was already in the lockfile transitively, so nothing new is downloaded.
  • CLI runs restore default SIGPIPE handling, so aura … | head exits quietly instead of panicking.

Testing

• cargo clippy --workspace --all-targets -D warnings, cargo fmt --check and cargo test --workspace pass. There are 24 new keymap unit tests: parsing, merge, warnings, and the file editor (format preservation, wizard key-set semantics, merge, document, export round-trip).
• Every aura keys command was tried by hand against separate test config directories.
• Not yet checked in the running GUI:
  • Keys work right after the window opens (X11 / Wayland / macOS / Windows)
  • Clicking and dragging still selects text with the root holding focus
  • ?, G and shift-tab match on non-US keyboard layouts
  • The help overlay scrolls when the window is short

Docs: docs/keybindings.md (new), plus updates to docs/configuration.md, docs/cli.md and the README.