List only after-1.0 work in the README roadmap (closes #208)

The README roadmap and the TODO.md Next Step still described finished
1.0 work as remaining. The roadmap now lists only work planned after
1.0. The security item says the encryption and blob-generation code was
reviewed before 1.0 with every finding fixed, and keeps an outside audit
as after-1.0 work rather than a blocker. The error-condition item is
gone because every failure case it listed now has a fault-injection
test. TODO.md says the 1.0 work is complete on next and that merging to
main and tagging are the owner's; Future Steps points to the roadmap.

Judgement call: dropped the human-readable size flags item; no command
flag takes a raw-integer size.

Model: opus-5-5

TODO.md

@@ -14,14 +14,11 @@ pre-1.0
 
 # Next Step
 
-Define the remaining scope for the first tagged release under the 1.0.0
-milestone, then cut that tag. The mechanism to cut it now exists and is
-exercised; what is left is the scope decision, which is the owner's.
-This step deliberately names one version number: it previously said
-"cut v0.1.0" while the `Makefile` baked in `1.0.0-rc.1` and the issue
-milestone said 1.0.0, and three different answers to "what is the next
-release" is exactly the contradiction
-[issue #65](https://git.eeqj.de/sneak/vaultik/issues/65) was filed over.
+The 1.0 work is complete on `next`: the scope settled on
+[issue #125](https://git.eeqj.de/sneak/vaultik/issues/125) was the work
+already planned for 1.0, and all of it has landed. The mechanism to cut
+the tag exists and is exercised; what is left is merging `next` to
+`main` and tagging, both the owner's.
 
 # Completed Steps
 
@@ -693,4 +690,5 @@ release" is exactly the contradiction
 
 # Future Steps
 
-None queued; the release-scoping item is now the Next Step.
+Work planned after 1.0 is listed in the README
+[roadmap](README.md#roadmap).