fix: list and open sessions across project directories

Sessions outside the server's launch directory were invisible and returned
404 on open, leaving the model picker empty. List without the SDK's
process-cwd filter and normalize working directories at the API boundary and
when reading stored session data, tolerating separator/normalization
differences (including Windows backslash vs forward slash). Requires Pi
coding agent SDK 0.78.0 or newer.

src/server/workingDirectory.test.ts

@@ -0,0 +1,56 @@
+import { join, sep } from "node:path";
+import { describe, expect, it } from "vitest";
+import { canonicalizeStoredCwd, cwdPathsEqual, normalizeRequestCwd } from "./workingDirectory.js";
+
+const absoluteBase = join(sep, "srv", "projects", "demo");
+
+describe("normalizeRequestCwd", () => {
+  it("returns absolute paths in canonical form", () => {
+    expect(normalizeRequestCwd(absoluteBase)).toBe(absoluteBase);
+    expect(normalizeRequestCwd(`${absoluteBase}${sep}`)).toBe(absoluteBase);
+    expect(normalizeRequestCwd(join(absoluteBase, ".", "nested", ".."))).toBe(absoluteBase);
+  });
+
+  it("treats Windows backslash and forward-slash paths as equal", () => {
+    if (process.platform !== "win32") return;
+    expect(normalizeRequestCwd("C:/Users/dev/project")).toBe("C:\\Users\\dev\\project");
+  });
+
+  it("rejects missing, empty, and non-string values", () => {
+    expect(() => normalizeRequestCwd(undefined)).toThrow("cwd is required");
+    expect(() => normalizeRequestCwd("")).toThrow("cwd is required");
+    expect(() => normalizeRequestCwd(42)).toThrow("cwd is required");
+  });
+
+  it("rejects relative paths instead of resolving them against the process cwd", () => {
+    expect(() => normalizeRequestCwd("relative/path")).toThrow("cwd must be an absolute path");
+    expect(() => normalizeRequestCwd(".")).toThrow("cwd must be an absolute path");
+  });
+});
+
+describe("canonicalizeStoredCwd", () => {
+  it("canonicalizes absolute paths", () => {
+    expect(canonicalizeStoredCwd(`${absoluteBase}${sep}`)).toBe(absoluteBase);
+  });
+
+  it("preserves legacy empty and relative values instead of resolving against the process cwd", () => {
+    expect(canonicalizeStoredCwd("")).toBe("");
+    expect(canonicalizeStoredCwd("relative/path")).toBe("relative/path");
+  });
+});
+
+describe("cwdPathsEqual", () => {
+  it("matches paths that differ only by normalization", () => {
+    expect(cwdPathsEqual(absoluteBase, `${absoluteBase}${sep}`)).toBe(true);
+    expect(cwdPathsEqual(absoluteBase, join(absoluteBase, "."))).toBe(true);
+  });
+
+  it("treats Windows backslash and forward-slash paths as equal", () => {
+    if (process.platform !== "win32") return;
+    expect(cwdPathsEqual("C:\\Users\\dev\\project", "C:/Users/dev/project")).toBe(true);
+  });
+
+  it("distinguishes different paths", () => {
+    expect(cwdPathsEqual(join(absoluteBase, "a"), join(absoluteBase, "b"))).toBe(false);
+  });
+});