Drop the TODO.md section numbers from 26 files

Eighty-five comments cited section numbers -- 1.1, 2.2.6, 3.6 -- from a
numbering the file had already abandoned before the move to the tracker. They
label completed work, so the pointer was the only wrong part.

The citation is removed and the sentence kept, which is what issue #27
recommended: these are labels, not references, and a label carrying a
version-dependent pointer goes stale again at the next reorganisation. Where a
pointer earns its place it names what actually holds the content now --
UPGRADING.md for the confirmed defects, libakerror #15 for the target
namespacing, issue #7 for the mutation survivors.

README.md and akstdlib.h sent readers to TODO.md for 'what is still open';
they name the tracker.

Verified: cmake --build build && ctest --test-dir build, 19/19.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Co-Authored-By: Andrew Kesterson <andrew@aklabs.net>

tests/test_stream.c

@@ -1,7 +1,7 @@
 /*
  * Stream wrappers: aksl_fopen / aksl_fread / aksl_fwrite / aksl_fclose.
  *
- * TODO.md section 1.2, now complete. The happy paths, the round trip, every
+ * Stream wrappers, complete. The happy paths, the round trip, every
  * NULL guard, both stream-error statuses, the transferred-member count that
  * aksl_fread and aksl_fwrite report through nmemb_out, and the three cases that
  * needed a hostile file to produce: a mode-denied path (EACCES), a full device
@@ -81,7 +81,7 @@ static int test_fopen_rejects_null_arguments(void)
 
     AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fopen(path, "r", NULL),
 				   AKERR_NULLPOINTER, "fp=");
-    /* TODO.md 2.2.2: both of these used to go straight through to fopen(3). */
+    /* both of these used to go straight through to fopen(3). */
     AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fopen(NULL, "r", &fp),
 				   AKERR_NULLPOINTER, "pathname=");
     AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fopen(path, NULL, &fp),
@@ -144,7 +144,7 @@ static int test_fread_short_read_is_eof_and_reports_the_count(void)
     AKSL_CHECK_OK(aksl_fopen(path, "r", &fp));
     AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fread(buf, 1, sizeof(buf), fp, &moved),
 				   AKERR_EOF, "EOF");
-    /* TODO.md 2.2.3: this is what the caller could not previously find out. */
+    /* this is what the caller could not previously find out. */
     AKSL_CHECK(moved == 4);
     AKSL_CHECK_OK(aksl_fclose(fp));
 
@@ -160,7 +160,7 @@ static int test_fread_short_read_is_eof_and_reports_the_count(void)
  *
  * That is a change from the old wrapper, which read ferror() and reported
  * AKERR_IO without ever consulting errno. Routing it through AKSL_ERRNO_OR
- * (TODO.md 2.2.1) keeps AKERR_IO as the fallback for the case where the stream
+ * keeps AKERR_IO as the fallback for the case where the stream
  * is in error and errno says nothing, and hands back the real reason otherwise.
  */
 static int test_fread_from_write_only_stream_reports_errno(void)
@@ -194,7 +194,7 @@ static int test_fread_rejects_null_arguments(void)
 
     AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fread(buf, 1, sizeof(buf), NULL, &moved),
 				   AKERR_NULLPOINTER, "fp=");
-    /* TODO.md 2.2.3: ptr was never checked in either direction. */
+    /* ptr was never checked in either direction. */
     AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fread(NULL, 1, sizeof(buf), fp, &moved),
 				   AKERR_NULLPOINTER, "ptr=");
     AKSL_CHECK_STATUS_MSG_CONTAINS(aksl_fread(buf, 1, sizeof(buf), fp, NULL),