♻️ Move script-header rationale into development/

branch.sh, finish.sh, release.sh, runner-image.sh and release-notes.sh
carried multi-paragraph 'how we got here / rejected' essays in comments. They
now live in the matching development/ category file, and each script keeps a
one-line pointer so the rationale is single-homed and cannot drift.

scripts/finish.sh

@@ -4,29 +4,14 @@ set -eu
 
 # Feature-finish front door. Run as `npm run create:finish`.
 #
-# Why this exists: `create:branch` opens a unit of work, but the close half
-# (`git checkout main && git merge --no-ff <branch>`) stayed prose in the
-# branching model, so it drifted per contributor and per session. This is the
-# mirror image of `create:branch`: it asserts the same preconditions (clean
-# tree, no in-progress operation, `main` matching its upstream), merges the
-# current `feature/`/`fix/`/`chore/` branch into `main`, proves the result with
-# `npm run verify`, and only then deletes the branch.
+# Mirror image of `create:branch`: asserts the merge-side preconditions, merges
+# the current `feature/`/`fix/`/`chore/` branch into `main` with `--no-ff`,
+# proves the result with `npm run verify`, and only then deletes the branch. The
+# push is owned by `create:release`, so the merge stays local and reviewable.
+# On a conflict it aborts and returns to the feature branch.
 #
-# `create:branch`'s comment argued against wrapping the merge as "judgment —
-# review the diff yourself". That judgment still lives here, just moved: the
-# maintainer reviews the handover *before* invoking this, and the script only
-# commits the merge, never the push. The push is owned by `create:release`, so
-# the release commit and its tag leave together and a local merge stays
-# reviewable (and can be reverted with `git revert -m 1`) until then. `--no-ff`
-# keeps the unit of work visible in `git log`.
-#
-# Unlike `create:branch` a stale `main` is fast-forwarded instead of refused:
-# the tree is clean (checked above) and `main` is not the checked-out branch
-# yet, so there is no local state to lose. True divergence (local commits *and*
-# upstream commits) is still refused — that needs a human.
-#
-# On a merge conflict we abort and return to the feature branch, so a failed
-# finish never strands you on a half-merged `main`.
+# Rationale and the rejected alternatives: development/workflow.md § Branching
+# model.
 
 BASE="main"
 PREFIXES="feature fix chore"