feat(coding-agent): implemented read-to-open tool aliasing in runtime

- Canonicalized file and CLI defaults from `read` to `open` across tool registration and prompts.
- Added `resolveToolAlias()` and applied alias-normalized tool selection so legacy `read` maps to `open`.
- Updated runtime, UI, and export layers to treat `open` as first-class while preserving `read` compatibility.
- Renamed read prompt docs to `open.md`/`open-chunk.md` and refreshed system guidance to recommend `open`.
- Updated tool-related tests and expectations from `read` to `open` (including test fixtures and aliases).

packages/coding-agent/src/modes/components/session-observer-overlay.ts

@@ -342,7 +342,8 @@ export class SessionObserverOverlayComponent extends Container {
 	#formatToolArgs(toolName: string, args: Record<string, unknown>): string {
 		// Show the most relevant arg for common tools
 		switch (toolName) {
-			case "read":
+			case "read": // legacy alias
+			case "open":
 				return args.path ? `path: ${args.path}` : "";
 			case "write":
 				return args.path ? `path: ${args.path}` : "";

packages/coding-agent/src/modes/components/tree-selector.ts

@@ -637,7 +637,8 @@ class TreeList implements Component {
 
 	#formatToolCall(name: string, args: Record<string, unknown>): string {
 		switch (name) {
-			case "read": {
+			case "read": // legacy alias
+			case "open": {
 				const path = shortenPath(String(args.path || args.file_path || ""));
 				const offset = args.offset as number | undefined;
 				const limit = args.limit as number | undefined;