feat: add searchable command palette

README.md

@@ -17,6 +17,7 @@ Without a file, vamp opens an unnamed buffer. A nonexistent file opens an empty
 
 | Mode | Keys |
 | --- | --- |
+| All modes | Ctrl+p opens the command palette; type to filter, Up/Down or Ctrl+k/Ctrl+n select, Enter accepts, Esc/Ctrl+p cancels |
 | Normal | `i` insert before each caret; `a` insert after each caret; `o`/`O` open lines below/above |
 | Normal, Visual | `I` (Shift+i) / `A` (Shift+a) insert at first nonblank / line end; Visual splits each touched row into a caret first |
 | Normal | `h`/`j`/`k`/`l` or arrows move every caret; `0`/`$` or Home/End |
@@ -62,11 +63,21 @@ Commands: `:w [path]`, `:q`, `:q!`, `:wq [path]`, `:plugins`, and `:plugin-comma
 
 Paste is backend input: it is ignored in Normal, Command, Search, and Visual modes, and inserts literal text in Insert mode, with CRLF/CR normalization and a 4 MiB limit. Pasted text is one undo action, separate from typing before and after it. Rejected paste reports an error without changing text, cursor, mode, or pending insert history. Internal clipboard actions are separate from `Input::Paste` and use already-validated buffer text.
 
+### Command palette
+
+Ctrl+p opens a searchable overlay without leaving the current mode. It lists core actions and registered Ex/plugin commands with their owner, effective bindings in the current mode, and eligible modes. Disabled or overridden bindings are not advertised; actions with no key remain available through the palette. Mode-ineligible entries are dimmed and cannot execute. Retired plugin commands disappear.
+
+Search is case-insensitive: every whitespace-separated query token must occur in the command name, human-readable label, or owner. Results have a stable label/name order. Up/Down or Ctrl+k/Ctrl+n wrap through results; Backspace removes a whole grapheme. Enter with no match or an ineligible selection leaves the palette open. Bracketed paste is ignored while the palette is open.
+
+Accepting a core action executes it in the underlying mode, including Visual edits and Insert-mode actions. Accepting an Ex/plugin command is available only in Normal mode and opens a prefilled `:` prompt; add arguments if needed, then Enter executes through the usual session dispatch. Choosing `q!` therefore does not immediately discard changes.
+
+Esc or Ctrl+p cancels without changing text, selections, the previous command/search prompt, or pending Insert history. The opening key can be remapped with `config.core.palette`; navigation and cancellation inside the palette are fixed. The TUI uses a constraint-based modal panel, keeps the selected result visible, and prioritizes the query on tiny terminals.
+
 ## Module seams
 
 One crate, four modules, no workspace or frontend-specific types in the editing backend:
 
-- `editor`: owns buffer, the primary cursor and selection set, modes and internal clipboard fragments, search state/navigation and grapheme-coordinate range presentation, key notation and binding resolution, modal paste policy, undo/redo, saving, command ownership, capabilities, and validated edit effects. Its low-level interface returns an `Invocation` when an external command is selected.
+- `editor`: owns buffer, the primary cursor and selection set, modes and internal clipboard fragments, search state/navigation and grapheme-coordinate range presentation, action metadata and command-palette state/filtering, key notation and binding resolution, modal paste policy, undo/redo, saving, command ownership, capabilities, and validated edit effects. Its low-level interface returns an `Invocation` when an external command is selected.
 - `session`: `EditorSession` owns the editor and its Ruby hosts together. It loads configuration, registers eligible plugins before installing bindings, executes selected commands, and retires both host and command ownership on invocation or effect-validation failure.
 - `tui`: translates terminal events to session input, renders read-only editor state, and advertises `text` and `styled_text` capabilities. It has no plugin lifecycle callback, host storage, or paste acceptance policy.
 - `ruby`: evaluates configuration and runs isolated plugin hosts. Protocol, deadlines, and process cleanup stay inside this module.
@@ -74,6 +85,7 @@ One crate, four modules, no workspace or frontend-specific types in the editing
 
 Frontends drive `EditorSession::handle` or `execute` and inspect `editor()`; there is no mutable editor getter that could independently alter plugin registration. Pasted text uses `Input::Paste(String)` through the same input seam as keys. Plugin effects are applied internally so a rejected result also retires its owner; there is no generic frontend effects entry point.
 Frontends inspect `selections()` for document-ordered, end-exclusive Visual ranges of grapheme coordinates (empty outside Visual), `carets()` for all active cursors in document order, `cursor()` for the primary, and `selection_count()` for the total target count. A range ending at the next row's column 0 includes the previous row's newline; an empty final-row range contains no text. Selection normalization, clipboard contents, edit planning, and history remain inside the editor module.
+Frontends inspect `palette()` for the optional read-only query, filtered command entries, selected index, effective bindings, and eligibility. Palette input handling and acceptance stay in the editor; registered command execution stays in the session.
 
 The terminal adapter owns raw mode, alternate-screen state, bracketed paste, and its panic hook for one session lifetime. Entry failure, normal return, I/O errors, and unwinding panics restore the caller's hook; active-terminal cleanup runs before caller panic diagnostics. Panics retain their original payload and propagate rather than being swallowed. Terminal state and panic hooks are process-global: run one TUI at a time and do not replace its hook while that session is active.
 
@@ -126,7 +138,7 @@ Terminals share `ctrl+h` with `backspace`, `ctrl+i` with `tab`, and `ctrl+j`/`ct
 | Normal, Insert, Visual | `word_next`, `word_previous`, `word_end`, `big_word_next`, `big_word_previous`, `big_word_end` |
 | Normal, Insert | `delete` |
 | Visual | `copy`, `cut`, `change`, `select_lines`, `select_next`, `skip_occurrence`, `select_all` |
-| Normal, Insert, Command, Search, Visual | `normal` |
+| Normal, Insert, Command, Search, Visual | `normal`, `palette` |
 | Insert, Command, Search | `backspace` |
 | Insert | `newline` |
 | Command, Search | `submit` |