feat(terminal): resolve relative path links against the pane's current directory

A relative path printed in the terminal was resolved against the session's
workingDir, which is fixed at create time and never follows a cd. In a shell
that moved into a subdirectory or a sibling repo, the link opened the wrong
file or reported "File not found".

The pane-exit watcher's batched list-panes read already carries
#{pane_current_path}. derivePaneCurrentPaths() turns those rows into one
directory per single-pane session, TmuxManager.getPaneCurrentPath() serves it
from memory, and the server applies it on the existing paneExitsUpdated tick
as SessionState.cwd, broadcasting only on a change. No new tmux call, no new
SSE event. A failed read keeps the previous answers.

Session.setCwd() uses the paneExit scoping rule: remote and Docker sessions
never get a cwd (their local pane runs the ssh or docker exec client), nor do
direct-PTY or rediscovered sessions. The value is runtime-only.

In the browser, relativeResolutionBase() picks the live cwd when known and
workingDir otherwise. It only changes the base a relative path joins: the
result is routed as before, so a target outside the workspace still goes
through the attachment routes, and file-content/file-raw are unchanged.

src/web/server.ts

@@ -2812,13 +2812,22 @@ export class WebServer extends EventEmitter {
   private applyPaneExits(): void {
     const getPaneExit = this.mux.getPaneExit?.bind(this.mux);
     if (!getPaneExit) return;
+    const getPaneCurrentPath = this.mux.getPaneCurrentPath?.bind(this.mux);
     for (const session of this.sessions.values()) {
       const muxName = session.muxName;
       // No pane, so nothing to report — and `setPaneExit()` would force UNKNOWN
       // for such a session anyway.
       if (!muxName) continue;
-      if (!session.setPaneExit(getPaneExit(muxName))) continue;
-      this.persistSessionState(session);
+      // The pane's live directory rides the same read: it is the base a relative
+      // path printed in the terminal resolves against. A session missing from
+      // the read keeps its last answer (a failed read reports nothing).
+      const cwd = getPaneCurrentPath?.(muxName);
+      const cwdChanged = cwd !== undefined && session.setCwd(cwd);
+      if (session.setPaneExit(getPaneExit(muxName))) {
+        this.persistSessionState(session);
+      } else if (!cwdChanged) {
+        continue;
+      }
       this.broadcastSessionStateDebounced(session.id);
     }
     this.closeCleanlyExitedSessions();