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_memory.c

@@ -1,8 +1,8 @@
 /*
- * Memory wrappers -- TODO.md section 1.1, now complete, plus the additions from
+ * Memory wrappers, complete, plus the additions from
  * section 3.1.
  *
- * The three cases 1.1 left open are all pinned here: malloc(0) is AKERR_VALUE
+ * The three cases the wrapper plan left open are all pinned here: malloc(0) is AKERR_VALUE
  * rather than whatever errno happened to hold when the platform's malloc(0)
  * returned NULL; an allocation the system cannot satisfy reports ENOMEM and
  * leaves *dst NULL rather than garbage; and overlapping memcpy is refused with
@@ -32,7 +32,7 @@ static int test_malloc_rejects_null_destination(void)
 }
 
 /*
- * TODO.md 1.1 asked for this contract to be pinned down. malloc(0) is allowed to
+ * The wrapper plan asked for this contract to be pinned down. malloc(0) is allowed to
  * return either a unique pointer or NULL, and a NULL there is not a failure and
  * need not set errno -- so the old wrapper could raise an error whose status was
  * 0, which every DETECT downstream reads as success while the context holds a
@@ -296,7 +296,7 @@ static int test_memcpy_zero_length_is_noop(void)
 }
 
 /*
- * TODO.md 1.1's open question, decided: overlap is AKERR_VALUE. memcpy(3) calls
+ * The wrapper plan's open question, decided: overlap is AKERR_VALUE. memcpy(3) calls
  * it undefined behaviour, which in practice means "works until the day a
  * compiler version or a length changes and it does not". Callers who mean to
  * overlap want aksl_memmove, and the message says so.