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.ts

@@ -0,0 +1,45 @@
+import { isAbsolute, resolve } from "node:path";
+
+/**
+ * Working-directory normalization boundaries.
+ *
+ * Cwd strings reach the server from three kinds of sources with different trust:
+ *
+ * 1. HTTP requests (web UI, federation proxies): normalize strictly with
+ *    `normalizeRequestCwd` at route parsing. Relative paths are rejected instead
+ *    of being silently resolved against the daemon's own working directory.
+ * 2. Data pi-web writes itself (archive store records): canonicalized on write
+ *    and on load with `canonicalizeStoredCwd`, so internal `===` comparisons are
+ *    safe by construction.
+ * 3. Data other writers own (Pi session file headers via the SDK): canonicalized
+ *    on read at the gateway, and compared tolerantly with `cwdPathsEqual` where a
+ *    raw value can still appear (e.g. runtime cwd of sessions opened from files).
+ *
+ * Inside these boundaries, plain string equality on cwd values is safe.
+ */
+
+/**
+ * Strictly normalize a client-supplied working directory at an HTTP boundary.
+ * Throws for non-string, empty, or relative input; returns the resolved
+ * (separator- and trailing-slash-normalized) absolute path otherwise.
+ */
+export function normalizeRequestCwd(cwd: unknown): string {
+  if (typeof cwd !== "string" || cwd === "") throw new Error("cwd is required");
+  if (!isAbsolute(cwd)) throw new Error("cwd must be an absolute path");
+  return resolve(cwd);
+}
+
+/**
+ * Leniently canonicalize a working directory loaded from stored data.
+ * Absolute paths are resolved to canonical form; anything else (legacy empty or
+ * relative values) is preserved as-is so a single bad record cannot fail a whole
+ * load, and never silently resolves against this process's working directory.
+ */
+export function canonicalizeStoredCwd(cwd: string): string {
+  return isAbsolute(cwd) ? resolve(cwd) : cwd;
+}
+
+/** Compare two working-directory paths, tolerating separator and normalization differences (e.g. Windows backslash vs forward slash). */
+export function cwdPathsEqual(a: string, b: string): boolean {
+  return resolve(a) === resolve(b);
+}