Remove TODO.md; track open work in the issues (closes #76)

TODO.md is deleted and the README TODO section now only points to the
issue tracker, where open work and open design questions live from now
on. AGENTS.md says so too, and says this overrides the shared policy's
README todo list for this repo. The README Open Questions section
becomes Original Design Questions, each noting where it now stands.

Every open item in both lists was already done or already owned by an
issue, apart from one, now #121,
and the chunk checksum question, now on
#81.

Model: opus-5-5

AGENTS.md

@@ -29,4 +29,6 @@ source for coding standards, formatting, linting, and workflow rules.
 - The format specification is in `FORMAT.md`.
 - Open work, open design questions included, is tracked only in the repo's
   issues: https://git.eeqj.de/sneak/mfer/issues. There is no `TODO.md` and no
-  TODO list in `README.md`; do not add either.
+  TODO list in `README.md`; do not add either. For this repo this overrides the
+  `REPO_POLICIES.md` rule to put the todo list in the README, per sneak's
+  ruling: https://git.eeqj.de/sneak/mfer/issues/76#issuecomment-118130.

README.md

@@ -157,18 +157,23 @@ The manifest file would do several important things:
     - metadata size should not be used as an excuse to sacrifice utility (such
       as providing checksums over each chunk of a large file)
 
-# Open Questions
+# Original Design Questions
+
+These were the open questions when the project started; open design questions
+are now tracked only in the [issues](https://git.eeqj.de/sneak/mfer/issues).
 
 - Should the manifest file include checksums of individual file chunks, or just
-  for the whole assembled file?
-
-    - If so, should the chunksize be fixed or dynamic?
+  for the whole assembled file? If so, should the chunk size be fixed or
+  dynamic? Still open, on
+  [issue 81](https://git.eeqj.de/sneak/mfer/issues/81#issuecomment-118698).
 
 - Should the manifest signature format be GnuPG signatures, or those from
   OpenBSD's signify (of which there is a good
-  [golang implementation](https://github.com/frankbraun/gosignify)?
+  [golang implementation](https://github.com/frankbraun/gosignify))? Still open,
+  as question 10 on [issue 82](https://git.eeqj.de/sneak/mfer/issues/82).
 
-- Should the on-disk serialization format be proto3 or json?
+- Should the on-disk serialization format be proto3 or json? Settled: it is
+  proto3, see `FORMAT.md` and `mfer/mf.proto`.
 
 # Tool Examples