feat(ai-conversations-browser): dired-style browser for saved GPTel conversations

`cj/gptel-load-conversation` prompts via `completing-read`.  A
dedicated browser shows what each conversation is about at a
glance and supports single-key load / delete / rename without
having to scroll a minibuffer list.

New module `modules/ai-conversations-browser.el` +
`cj/gptel-browse-conversations` entry point bound to `C-; a b`
("browse conversations").  Opens `*GPTel-Conversations*` in
`cj/gptel-browser-mode` (a `special-mode` derivative).

Each row shows date, time, topic slug, and a preview of the most
recent message (length configurable via
`cj/gptel-browser-preview-length`, default 60 chars).  Rows sort
newest first.

In the browser:
- `RET` / `l`: load the conversation (delegates to
  `cj/gptel-load-conversation` with the file pre-selected via a
  `cl-letf` stub on `completing-read` so the user isn't prompted
  twice), then bury the window.
- `d`: delete the file under point after `y-or-n-p` confirmation,
  re-render.
- `r`: rename the file under point.  Preserves the timestamp,
  slugifies the new topic, refuses unchanged input and existing
  targets.
- `g`: refresh.
- `n` / `p`: next / previous row.
- `q`: quit-window.

21 tests cover the helpers (topic parsing, header stripping,
preview shaping for truncate / short / empty cases, row-for-file
with conversation + non-conversation filenames, rows enumeration,
render output for empty + populated cases, newest-first sort,
rename-target preservation of timestamp + slug, rename-target
error on missing timestamp) and the file-touching actions (delete
with y, cancel with n, rename, rename-on-empty-line error).

1 files changed, 3 insertions, 0 deletions

diff --git a/modules/ai-config.el b/modules/ai-config.el
index c7a14cae..9ac00bfe 100644
--- a/modules/ai-config.el
+++ b/modules/ai-config.el
@@ -37,6 +37,7 @@
 (autoload 'cj/gptel-quick-ask "ai-quick-ask" "One-shot quick-ask in a transient buffer." t)
 (autoload 'cj/gptel-rewrite-with-directive "ai-rewrite" "Pick a directive and run gptel-rewrite on the region." t)
 (autoload 'cj/gptel-rewrite-redo-with-different-directive "ai-rewrite" "Re-run the previous rewrite with a different directive." t)
+(autoload 'cj/gptel-browse-conversations "ai-conversations-browser" "Browse saved GPTel conversations." t)
 
 ;;; ------------------------- AI Config Helper Functions ------------------------
 
@@ -508,6 +509,7 @@ Works for any buffer, whether it's visiting a file or not."
   "d" #'cj/gptel-delete-conversation ;; delete conversation
   "." #'cj/gptel-add-this-buffer     ;; add buffer to context
   "f" #'cj/gptel-add-file            ;; add a file to context
+  "b" #'cj/gptel-browse-conversations ;; browse saved conversations
   "l" #'cj/gptel-load-conversation   ;; load and continue conversation
   "m" #'cj/gptel-change-model        ;; change the LLM model
   "p" #'gptel-system-prompt          ;; change prompt
@@ -526,6 +528,7 @@ Works for any buffer, whether it's visiting a file or not."
     "C-; a A" "toggle autosave"
     "C-; a B" "switch backend"
     "C-; a M" "gptel menu"
+    "C-; a b" "browse conversations"
     "C-; a d" "delete conversation"
     "C-; a ." "add buffer"
     "C-; a f" "add file"