fix: name the pane directory field paneCwd and apply the review items for #740

`cwd` beside the fixed `workingDir` reads ambiguously on a public API surface, and
`paneCwd` says where the value comes from, like `paneExit`. Also pin the field on
the payload the browser really receives (getSessionStateWithRespawn), and give the
pane-directory text its own architecture-invariants paragraph.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/web/public/constants.js

@@ -2431,23 +2431,23 @@ function resolveLinkedFilePath(filePath, workingDir) {
  *
  * `workingDir` is recorded once at create time and never follows a `cd`, so it
  * stops describing where a shell (or an agent that changed directory) really
- * is. `session.cwd` is the pane's live `#{pane_current_path}`, published by the
+ * is. `session.paneCwd` is the pane's live `#{pane_current_path}`, published by the
  * server from its pane read. It only changes which BASE a relative path joins;
  * the result is then routed like any other path, so a target outside the
  * workspace still goes through the attachment routes.
  *
- * Remote and Docker sessions are excluded (the server never sends them a cwd,
+ * Remote and Docker sessions are excluded (the server never sends them a paneCwd,
  * and this checks again): their local pane runs the ssh / docker-exec CLIENT,
- * so its directory says nothing about the agent. An unknown cwd falls back to
+ * so its directory says nothing about the agent. An unknown paneCwd falls back to
  * `workingDir`.
  *
- * @param {{workingDir?: string, cwd?: string, remote?: unknown, docker?: unknown}} [session]
+ * @param {{workingDir?: string, paneCwd?: string, remote?: unknown, docker?: unknown}} [session]
  * @returns {string|undefined}
  */
 function relativeResolutionBase(session) {
   if (!session) return undefined;
-  const cwd = session.cwd;
-  if (!session.remote && !session.docker && typeof cwd === 'string' && cwd.startsWith('/')) return cwd;
+  const paneCwd = session.paneCwd;
+  if (!session.remote && !session.docker && typeof paneCwd === 'string' && paneCwd.startsWith('/')) return paneCwd;
   return session.workingDir;
 }
 

src/web/server.ts

@@ -2866,10 +2866,10 @@ export class WebServer extends EventEmitter {
       // or empty read and carries a blank `#{pane_current_path}` forward, so an
       // `undefined` here means an authoritative read listed no single directory
       // for the session (split into several panes, or gone from the socket).
-      const cwdChanged = getPaneCurrentPath ? session.setCwd(getPaneCurrentPath(muxName)) : false;
+      const paneCwdChanged = getPaneCurrentPath ? session.setPaneCwd(getPaneCurrentPath(muxName)) : false;
       if (session.setPaneExit(getPaneExit(muxName))) {
         this.persistSessionState(session);
-      } else if (!cwdChanged) {
+      } else if (!paneCwdChanged) {
         continue;
       }
       this.broadcastSessionStateDebounced(session.id);