clang-tidy: sync argument names in prototype and definition

Discovered with clang-tidy checker
`readability-inconsistent-declaration-parameter-name`.

Also:
- do not enforce the above because of inconsistencies still present
  between public API prototypes and definitions. (Also betwen man page
  protos, and man page examples, and other parts of the code, e.g.
  `easy` vs `curl` vs `d` vs `handle`) Perhaps subject for a future
  effort:
  https://github.com/curl/curl/actions/runs/22166472728/job/64094691653
- enable and fix `readability-named-parameter` where missing.

Refs:
https://clang.llvm.org/extra/clang-tidy/checks/readability/inconsistent-declaration-parameter-name.html
https://clang.llvm.org/extra/clang-tidy/checks/readability/named-parameter.html

Closes #20624

lib/sendf.h

@@ -58,7 +58,7 @@ struct Curl_easy;
  * Write `len` bytes at `prt` to the client. `type` indicates what
  * kind of data is being written.
  */
-CURLcode Curl_client_write(struct Curl_easy *data, int type, const char *ptr,
+CURLcode Curl_client_write(struct Curl_easy *data, int type, const char *buf,
                            size_t len) WARN_UNUSED_RESULT;
 
 /**
@@ -140,7 +140,7 @@ struct Curl_cwriter {
  */
 CURLcode Curl_cwriter_create(struct Curl_cwriter **pwriter,
                              struct Curl_easy *data,
-                             const struct Curl_cwtype *ce_handler,
+                             const struct Curl_cwtype *cwt,
                              Curl_cwriter_phase phase);
 
 /**
@@ -298,7 +298,7 @@ void Curl_creader_clear_eos(struct Curl_easy *data,
  */
 CURLcode Curl_creader_create(struct Curl_creader **preader,
                              struct Curl_easy *data,
-                             const struct Curl_crtype *cr_handler,
+                             const struct Curl_crtype *crt,
                              Curl_creader_phase phase);
 
 /**