refactor(ai-vterm): rename Claude-specific names to a generic "agent"

I may add other terminal agents to this launcher (aider, an open-source LLM TUI), so the buffer prefix, the user knob, and the internal helpers shouldn't say "Claude". The module name (ai-vterm) and the `cj/ai-vterm-*` customs were already generic. This finishes the job:

- buffer prefix `claude [<basename>]` -> `agent [<basename>]` (the `defconst` and the matching display-buffer-alist regex move together)
- `cj/ai-vterm-claude-command` -> `cj/ai-vterm-agent-command` (the default still runs the `claude` CLI, with a docstring note on swapping it)
- `cj/--ai-vterm-claude-buffers` / `-displayed-claude-window` / `-reuse-existing-claude` -> `-agent-*`, and their test files renamed to match
- prose in the module commentary and docstrings, plus the matching test docstrings and buffer-name literals

`vterm-config.el` hardcodes the same buffer prefix in `cj/--vterm-toggle-buffer-p` (F12 excludes agent buffers from its candidate set), so that literal moved too. Collapsing it into the shared `cj/--ai-vterm-name-prefix` is a cleanup for another day.

After a reload, a project's buffer opens as `agent [foo]` instead of `claude [foo]`. Old buffers keep their names until killed. I also corrected two stale `eshell-vterm-config.el` references in ai-vterm.el docstrings (that module was split into `vterm-config.el`).

Two things keep saying "Claude": the `cj/ai-vterm-agent-command` default value (the actual CLI), and the "Claude Code" example in `vterm-config.el`'s cursor-restore docstring (a concrete TUI example, not branding).

90 tests pass. `make validate-modules` clean.

1 files changed, 5 insertions, 5 deletions

diff --git a/tests/test-vterm-tmux-history.el b/tests/test-vterm-tmux-history.el
index db82176f..901d96c9 100644
--- a/tests/test-vterm-tmux-history.el
+++ b/tests/test-vterm-tmux-history.el
@@ -164,13 +164,13 @@ modern keyboards and was redundant."
   "Normal: an AI-vterm-named buffer still resolves by process TTY.
 
 The copy path belongs to `vterm-mode', not to `*vterm*'-named buffers.
-A buffer named like `claude [repo]' (ai-vterm.el's naming) is a
+A buffer named like `agent [repo]' (ai-vterm.el's naming) is a
 `vterm-mode' buffer and must inherit tmux history copy.  The pane lookup
 keys off the live process TTY, never the buffer name -- so the
 AI-vterm name neither helps nor blocks resolution."
-  (let ((claude (cj/test--make-fake-vterm-buffer "claude [emacs.d]")))
+  (let ((agent (cj/test--make-fake-vterm-buffer "agent [emacs.d]")))
     (unwind-protect
-        (with-current-buffer claude
+        (with-current-buffer agent
           (cl-letf (((symbol-function 'get-buffer-process)
                      (lambda (_buffer) 'fake-process))
                     ((symbol-function 'process-tty-name)
@@ -179,8 +179,8 @@ AI-vterm name neither helps nor blocks resolution."
                 '((("list-clients" "-F" "#{client_tty}\t#{pane_id}") 0
                    "/dev/pts/1\t%1\n/dev/pts/8\t%8\n"))
               (should (equal (cj/vterm--current-tmux-pane-id) "%8")))))
-      (when (buffer-live-p claude)
-        (kill-buffer claude)))))
+      (when (buffer-live-p agent)
+        (kill-buffer agent)))))
 
 (provide 'test-vterm-tmux-history)
 ;;; test-vterm-tmux-history.el ends here