Move the build, release, and acceptance docs to the documentation site

The documentation site, docs.forgefirm.org, is the one home for the
developer documentation. BUILD.md, kas/README.md, and docs/ACCEPTANCE.md
are on the site under Developers, and they are deleted here. Every
reference points at the site: README.md, BRINGUP.md, UPDATE-SYSTEM.md,
the kas configuration comments, release.sh, the CI workflow comments, and
the releases, forgetest, and bench READMEs.

BRINGUP.md: "Next work" item 16, step timing under CPU contention, is
closed; the video work resolved it. The items after it are renumbered.
CAMPAIGN-LOG.md records the closure.

Documentation and comments only. No layer content changes, so the
manifest identity of the next image does not change. No catalog
consequence.

.github/workflows/forgetest-ci.yml

@@ -11,7 +11,7 @@
 #  - coverage lint: every source path of every component pinned by the
 #    recipes must be selected by some catalog test's coverage globs (the
 #    tree manifest is generated from the pins with git - no Yocto build);
-#    enforced: an uncovered path fails the job (docs/ACCEPTANCE.md).
+#    enforced: an uncovered path fails the job (https://docs.forgefirm.org/developers/acceptance/).
 
 name: forgetest-ci
 

.github/workflows/yocto-cold-build.yml

@@ -31,7 +31,7 @@ jobs:
           path: forgefirm
 
       # The kas config references meta-openglow as a local sibling
-      # (kas/README.md "Push & release order" step 4 flips it to the
+      # (the release flow on the documentation site flips it to the
       # pinned-remote block at release time). Every source repo the recipes
       # build is fetched by pinned SRCREV; no other sibling is needed.
       - name: Checkout meta-openglow (sibling)