chore: drop non-code junk (pi-mono-reference, runtime state, root duplicates)

Remove files that should never have been tracked:

- pi-mono-reference/: 688-file copy of an upstream monorepo, zero imports,
  used only as offline human reference
- build/electron-builder.runtime.json: environment-specific build artifact
  with hardcoded local paths
- state/cancel-signal-state.json: runtime state written by the app
- prompt.txt, logo.svg (root): exact duplicates of the canonical copies
  under .planning/archive/ and assets/

Add state/ to .gitignore so future runtime state stays out.

pi-mono-reference/packages/tui/src/editor-component.ts

@@ -1,74 +0,0 @@
-import type { AutocompleteProvider } from "./autocomplete.js";
-import type { Component } from "./tui.js";
-
-/**
- * Interface for custom editor components.
- *
- * This allows extensions to provide their own editor implementation
- * (e.g., vim mode, emacs mode, custom keybindings) while maintaining
- * compatibility with the core application.
- */
-export interface EditorComponent extends Component {
-	// =========================================================================
-	// Core text access (required)
-	// =========================================================================
-
-	/** Get the current text content */
-	getText(): string;
-
-	/** Set the text content */
-	setText(text: string): void;
-
-	/** Handle raw terminal input (key presses, paste sequences, etc.) */
-	handleInput(data: string): void;
-
-	// =========================================================================
-	// Callbacks (required)
-	// =========================================================================
-
-	/** Called when user submits (e.g., Enter key) */
-	onSubmit?: (text: string) => void;
-
-	/** Called when text changes */
-	onChange?: (text: string) => void;
-
-	// =========================================================================
-	// History support (optional)
-	// =========================================================================
-
-	/** Add text to history for up/down navigation */
-	addToHistory?(text: string): void;
-
-	// =========================================================================
-	// Advanced text manipulation (optional)
-	// =========================================================================
-
-	/** Insert text at current cursor position */
-	insertTextAtCursor?(text: string): void;
-
-	/**
-	 * Get text with any markers expanded (e.g., paste markers).
-	 * Falls back to getText() if not implemented.
-	 */
-	getExpandedText?(): string;
-
-	// =========================================================================
-	// Autocomplete support (optional)
-	// =========================================================================
-
-	/** Set the autocomplete provider */
-	setAutocompleteProvider?(provider: AutocompleteProvider): void;
-
-	// =========================================================================
-	// Appearance (optional)
-	// =========================================================================
-
-	/** Border color function */
-	borderColor?: (str: string) => string;
-
-	/** Set horizontal padding */
-	setPaddingX?(padding: number): void;
-
-	/** Set max visible items in autocomplete dropdown */
-	setAutocompleteMaxVisible?(maxVisible: number): void;
-}