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, 12 insertions, 12 deletions

diff --git a/tests/test-ai-vterm--show-or-create.el b/tests/test-ai-vterm--show-or-create.el
index 3fee4883..0a3dbde5 100644
--- a/tests/test-ai-vterm--show-or-create.el
+++ b/tests/test-ai-vterm--show-or-create.el
@@ -3,7 +3,7 @@
 ;;; Commentary:
 ;; Tests the show-or-create branching:
 ;;
-;; - buffer absent          -> vterm called, claude command sent
+;; - buffer absent          -> vterm called, agent command sent
 ;; - buffer present, live   -> vterm not called, buffer displayed
 ;; - buffer present, dead   -> old buffer killed, vterm recreates
 ;;
@@ -58,7 +58,7 @@ VARS is a plist of capture variable names: :calls, :strings, :returns,
 
 (ert-deftest test-ai-vterm--show-or-create-creates-when-buffer-missing ()
   "Normal: no existing buffer -> vterm called once, launch cmd sent."
-  (let ((name "claude [normal-create-test]"))
+  (let ((name "agent [normal-create-test]"))
     (test-ai-vterm--cleanup name)
     (unwind-protect
         (test-ai-vterm--with-mock-vterm (:calls calls :strings strings
@@ -73,7 +73,7 @@ VARS is a plist of capture variable names: :calls, :strings, :returns,
 
 (ert-deftest test-ai-vterm--show-or-create-displays-existing-when-process-live ()
   "Normal: buffer exists with live process -> vterm not called."
-  (let ((name "claude [reuse-test]"))
+  (let ((name "agent [reuse-test]"))
     (test-ai-vterm--cleanup name)
     (unwind-protect
         (let ((buf (get-buffer-create name)))
@@ -89,7 +89,7 @@ VARS is a plist of capture variable names: :calls, :strings, :returns,
 
 (ert-deftest test-ai-vterm--show-or-create-recreates-when-process-dead ()
   "Boundary: buffer exists with dead process -> killed and recreated."
-  (let ((name "claude [dead-test]"))
+  (let ((name "agent [dead-test]"))
     (test-ai-vterm--cleanup name)
     (unwind-protect
         (let ((stale (get-buffer-create name)))
@@ -111,17 +111,17 @@ VARS is a plist of capture variable names: :calls, :strings, :returns,
 Real `vterm' replaces the selected window's buffer as a side-effect of
 construction.  On a fresh-boot frame (one window showing the dashboard),
 that side-effect previously left the original window pointing at the new
-claude buffer; the dashboard was buried, the alist-routed split then
-created a second window also showing claude.  The wrapper must restore
+agent buffer; the dashboard was buried, the alist-routed split then
+created a second window also showing agent.  The wrapper must restore
 the original window state before `display-buffer' fires so dashboard
-stays put and the alist places claude into a fresh right-side split.
+stays put and the alist places agent into a fresh right-side split.
 
 This test stubs `vterm' to mimic the pop-to-buffer-same-window side-effect
 and asserts the originally-selected window still shows its original buffer
 after `cj/--ai-vterm-show-or-create' returns."
-  (let ((claude-name "claude [preserve-window-test]")
+  (let ((agent-name "agent [preserve-window-test]")
         (orig-name "*test-original-buffer*"))
-    (test-ai-vterm--cleanup claude-name)
+    (test-ai-vterm--cleanup agent-name)
     (when (get-buffer orig-name) (kill-buffer orig-name))
     (unwind-protect
         (save-window-excursion
@@ -139,14 +139,14 @@ after `cj/--ai-vterm-show-or-create' returns."
                   (lambda (_s &optional _) nil))
                  ((symbol-function 'vterm-send-return)
                   (lambda () nil)))
-              (cj/--ai-vterm-show-or-create "/tmp/preserve" claude-name)
+              (cj/--ai-vterm-show-or-create "/tmp/preserve" agent-name)
               (should (eq (window-buffer orig-win) orig-buf)))))
-      (test-ai-vterm--cleanup claude-name)
+      (test-ai-vterm--cleanup agent-name)
       (when (get-buffer orig-name) (kill-buffer orig-name)))))
 
 (ert-deftest test-ai-vterm--show-or-create-returns-buffer ()
   "Normal: return value is the vterm buffer."
-  (let ((name "claude [return-test]"))
+  (let ((name "agent [return-test]"))
     (test-ai-vterm--cleanup name)
     (unwind-protect
         (test-ai-vterm--with-mock-vterm (:calls _c :strings _s