Fix SDK tools to respect cwd option

Core tools now properly use the cwd passed to createAgentSession().
Added tool factory functions for SDK users who specify custom cwd with explicit tools.

Fixes #279

packages/coding-agent/src/core/tools/path-utils.ts

@@ -1,5 +1,6 @@
 import { accessSync, constants } from "node:fs";
 import * as os from "node:os";
+import { isAbsolute, resolve as resolvePath } from "node:path";
 
 const UNICODE_SPACES = /[\u00A0\u2000-\u200A\u202F\u205F\u3000]/g;
 const NARROW_NO_BREAK_SPACE = "\u202F";
@@ -32,17 +33,29 @@ export function expandPath(filePath: string): string {
 	return normalized;
 }
 
-export function resolveReadPath(filePath: string): string {
+/**
+ * Resolve a path relative to the given cwd.
+ * Handles ~ expansion and absolute paths.
+ */
+export function resolveToCwd(filePath: string, cwd: string): string {
 	const expanded = expandPath(filePath);
-
-	if (fileExists(expanded)) {
+	if (isAbsolute(expanded)) {
 		return expanded;
 	}
+	return resolvePath(cwd, expanded);
+}
 
-	const macOSVariant = tryMacOSScreenshotPath(expanded);
-	if (macOSVariant !== expanded && fileExists(macOSVariant)) {
+export function resolveReadPath(filePath: string, cwd: string): string {
+	const resolved = resolveToCwd(filePath, cwd);
+
+	if (fileExists(resolved)) {
+		return resolved;
+	}
+
+	const macOSVariant = tryMacOSScreenshotPath(resolved);
+	if (macOSVariant !== resolved && fileExists(macOSVariant)) {
 		return macOSVariant;
 	}
 
-	return expanded;
+	return resolved;
 }