Cut the narration from TODO.md and the script and Dockerfile comments (closes #49)

Completed Steps entries keep what landed, the traps, every disclosure
and every record that a check ran; the argument and history go, with
bare issue numbers turned into full links. Comment blocks in script/,
Dockerfile and Dockerfile.lint keep the trap and drop the defence of
past decisions. TODO.md Workflow now branches from next, targets next,
and leaves merging next to main to the owner. Only comments and
Markdown change.

Model: opus-5-5

script/docker

@@ -1,14 +1,9 @@
 #!/bin/sh
 # script/docker: build the Docker image tagged with the project name.
-# The tag comes from script/projectname.
-#
-# CHECK_EPOCH is passed for the same reason script/cibuild passes it:
-# without a fresh value Docker serves the gate layers from cache on an
-# unchanged tree and this exits 0 having run none of the lint stage's
-# gates, the markdown stage's prettier gate or the builder stage's test
-# gate. This is the set of gates a developer or reviewer runs by hand,
-# so a cached pass here is the most misleading result the repo can
-# produce. Dependency layers sit above the ARG and stay cached.
+# The tag comes from script/projectname. CHECK_EPOCH is passed for the
+# same reason script/cibuild passes it: without a fresh value an
+# unchanged tree is served from cache and this exits 0 having run no
+# gate.
 set -eu
 
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"