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/session/compaction/pruning.ts

@@ -18,7 +18,7 @@ export interface PruneConfig {
 export const DEFAULT_PRUNE_CONFIG: PruneConfig = {
 	protectTokens: 40_000,
 	minimumSavings: 20_000,
-	protectedTools: ["skill", "read"],
+	protectedTools: ["skill", "open", "read"],
 };
 
 export interface PruneResult {

packages/coding-agent/src/session/compaction/utils.ts

@@ -44,7 +44,8 @@ export function extractFileOpsFromMessage(message: AgentMessage, fileOps: FileOp
 		if (!path) continue;
 
 		switch (block.name) {
-			case "read":
+			case "read": // legacy alias
+			case "open":
 				fileOps.read.add(path);
 				break;
 			case "write":