gptel: checkdoc linting and indentation rules

* gptel.el (gptel-use-header-line, gptel--parse-buffer):
Docstrings.

* gptel-transient.el (gptel--transient-read-variable): Docstring.

* gptel-openai.el (gptel-make-openai, gptel-make-azure): Add
indent declaration.

* gptel-ollama.el (gptel-make-ollama): Add indent declaration.

* gptel-kagi.el (gptel-make-kagi): Add indent declaration.

* gptel-gemini.el (gptel-make-gemini): Add indent declaration.

gptel-gemini.el

@@ -135,6 +135,7 @@ alist, like:
 
 KEY (optional) is a variable whose value is the API key, or
 function that returns the key."
+  (declare (indent 1))
   (let ((backend (gptel--make-gemini
                   :name name
                   :host host

gptel-kagi.el

@@ -156,6 +156,7 @@ Example:
 -------
 
 (gptel-make-kagi \"Kagi\" :key my-kagi-key)"
+  (declare (indent 1))
   stream                                ;Silence byte-compiler
   (let ((backend (gptel--make-kagi
                   :name name

gptel-ollama.el

@@ -138,6 +138,7 @@ Example:
   :host \"localhost:11434\"
   :models \\='(\"mistral:latest\")
   :stream t)"
+  (declare (indent 1))
   (let ((backend (gptel--make-ollama
                   :name name
                   :host host

gptel-openai.el

@@ -142,6 +142,7 @@ alist, like:
 
 KEY (optional) is a variable whose value is the API key, or
 function that returns the key."
+  (declare (indent 1))
   (let ((backend (gptel--make-openai
                   :name name
                   :host host
@@ -201,6 +202,7 @@ Example:
  \"/openai/deployments/DEPLOYMENT_NAME/completions?api-version=2023-05-15\"
  :stream t
  :models \\='(\"gpt-3.5-turbo\" \"gpt-4\"))"
+  (declare (indent 1))
   (let ((backend (gptel--make-openai
                   :name name
                   :host host

gptel-transient.el

@@ -257,7 +257,10 @@ Customize `gptel-directives' for task-specific prompts."
 ;; ** Infixes for model parameters
 
 (defun gptel--transient-read-variable (prompt initial-input history)
-  "Read value from minibuffer and interpret the result as a Lisp object."
+  "Read value from minibuffer and interpret the result as a Lisp object.
+
+PROMPT, INITIAL-INPUT and HISTORY are as in the Transient reader
+documention."
   (ignore-errors
     (read-from-minibuffer prompt initial-input read-expression-map t history)))
 
@@ -402,7 +405,7 @@ will get progressively longer!"
                      (list (line-beginning-position) (line-end-position))))))
           ((member "y" args)
            (unless (car-safe kill-ring)
-             (user-error "`kill-ring' is empty!  Nothing to send."))
+             (user-error "`kill-ring' is empty!  Nothing to send"))
            (if current-prefix-arg
                (read-from-kill-ring "Prompt from kill-ring: ")
              (current-kill 0))))))

gptel.el

@@ -297,8 +297,7 @@ is only inserted in dedicated gptel buffers before the AI's response."
   :type '(alist :key-type symbol :value-type string))
 
 (defcustom gptel-use-header-line t
-  "Whether `gptel-mode' should use header-line for status
+  "Whether `gptel-mode' should use header-line for status information.
-information.
 
 When set to nil, use the mode line for (minimal) status
 information and the echo area for messages."
@@ -806,6 +805,7 @@ streamed, as in `gptel-stream'. Do not set this if you are
 specifying a custom CALLBACK!
 
 Model parameters can be let-bound around calls to this function."
+  (declare (indent 1))
   (let* ((gptel-stream stream)
          (start-marker
           (cond
@@ -985,8 +985,7 @@ there."
         (gptel--parse-buffer gptel-backend max-entries)))))
 
 (cl-defgeneric gptel--parse-buffer (backend max-entries)
-  "Parse the current buffer backwards from point and return a list
+  "Parse current buffer backwards from point and return a list of prompts.
-of prompts.
 
 BACKEND is the LLM backend in use.