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.

docs/wiki/Working-With-Files.md

@@ -87,7 +87,10 @@ detected at once would fork ten multi-minute converter processes.
 
 File paths in a session are links. That works in two places:
 
-- **In the terminal**, on any absolute path an agent prints.
+- **In the terminal**, on any path an agent or a command prints. A relative path (`src/app.ts`,
+  `../notes.md`) resolves against the directory the session's pane is in now, so after a `cd`
+  in a shell it opens the file there; until the pane reports a directory, and always for remote
+  SSH and Docker cases, it resolves against the session's working directory.
 - **In the response viewer**, where paths are usually written as prose or in backticks. They
   render as underlined monospace links. A Markdown link whose target is a path
   (`[report](/tmp/run/report.json)`, the way Codex cites files) opens the same way.