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/tools/python.ts

@@ -590,7 +590,8 @@ function formatStatusEvent(event: PythonStatusEvent, theme: Theme): string {
 
 	// Build description based on common fields
 	switch (op) {
-		case "read":
+		case "read": // legacy alias
+		case "open":
 			parts.push(`${data.chars} chars`);
 			if (data.path) parts.push(`from ${shortenPath(String(data.path))}`);
 			break;
@@ -794,7 +795,8 @@ function formatStatusEventExpanded(event: PythonStatusEvent, theme: Theme): stri
 		case "git_branch":
 			if (data.branches) addItems(data.branches as unknown[], b => String(b));
 			break;
-		case "read":
+		case "read": // legacy alias
+		case "open":
 		case "cat":
 		case "head":
 		case "tail":