feat(build): symlink website/releases/<tool>_alpha.html into dist instead of copying

Every plain `sh tool/build.sh` invocation now reasserts a relative symlink
website/releases/<tool>_alpha.html → ../../<tool>/dist/<tool>.html so the
alpha hyperlinks always serve whatever dist currently holds. Idempotent — git
sees no churn on rebuild. `--release alpha` still wins by overwriting the
symlink with a real "alpha · <date> · <sha>" file; the next plain build
re-symlinks it.

Five existing alpha files become typechanges (regular file → symlink) — the
one-time migration cost. The reassertion survives deployment because the
website is served directly from the working tree.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

archive/build.sh

@@ -85,4 +85,6 @@ echo "Wrote $output_html"
 
 if [ "$is_release" = "1" ]; then
     promote_release "archive"
+else
+    update_alpha "archive"
 fi

classifier/build.sh

@@ -83,4 +83,6 @@ echo "Wrote $output_html"
 
 if [ "$is_release" = "1" ]; then
     promote_release "classifier"
+else
+    update_alpha "classifier"
 fi

landing/build.sh

@@ -69,4 +69,6 @@ if [ "$is_release" = "1" ]; then
     # landing_stable.html at the customer deployment root, where the
     # project picker UI is useful (it queries zddc-server for the
     # project list). See AGENTS.md "Releasing — channels and layout".
+else
+    update_alpha "landing"
 fi

mdedit/build.sh

@@ -124,4 +124,6 @@ echo "Wrote $output_html ($(wc -c < "$output_html") bytes)"
 
 if [ "$is_release" = "1" ]; then
     promote_release "mdedit"
+else
+    update_alpha "mdedit"
 fi

shared/build-lib.sh

@@ -25,6 +25,18 @@
 #                                   driven by $channel and $build_version. For
 #                                   stable, also update the _stable.html
 #                                   symlink and create the git tag.
+#   update_alpha <tool>            — (re)point website/releases/<tool>_alpha.html
+#                                   as a relative symlink at the just-built dist
+#                                   file, so the site's alpha hyperlinks always
+#                                   serve whatever dist currently holds. Called
+#                                   automatically by each tool's build.sh on
+#                                   plain (non-release) builds. Idempotent —
+#                                   reasserting the link on every build leaves
+#                                   git clean. `--release alpha` still works:
+#                                   promote_release replaces the symlink with a
+#                                   real file labeled "alpha · <date> · <sha>"
+#                                   (a deliberate snapshot that persists until
+#                                   the next dev build re-symlinks).
 #
 # Channels and release args:
 #   <none>            dev build, dist/ only, label "Built: <ts> BETA" (red).
@@ -196,3 +208,20 @@ promote_release() {
     git -C "$root_dir" tag "${_tool}-v${build_version}"
     echo "Tagged ${_tool}-v${build_version} — run: git push --tags"
 }
+
+# (Re)point website/releases/<tool>_alpha.html at the just-built dist file via
+# a relative symlink, so the website's alpha hyperlinks always serve whatever
+# dist currently holds. Called by each tool's build.sh whenever a release is
+# NOT being cut. Idempotent: if the link already points at the right target,
+# git sees no change. `--release alpha` overwrites this link with a real file
+# (with the "alpha · date · sha" label); the next plain build re-symlinks it.
+# Reads $output_html and $root_dir from caller scope.
+update_alpha() {
+    _tool="$1"
+    _releases_dir="$root_dir/../website/releases"
+    _dist_basename=$(basename "$output_html")
+    _target="../../${_tool}/dist/${_dist_basename}"
+    mkdir -p "$_releases_dir"
+    (cd "$_releases_dir" && ln -sfn "$_target" "${_tool}_alpha.html")
+    echo "Linked ${_tool}_alpha.html -> $_target"
+}

transmittal/build.sh

@@ -167,4 +167,6 @@ echo "Wrote $output_html"
 
 if [ "$is_release" = "1" ]; then
     promote_release "transmittal"
+else
+    update_alpha "transmittal"
 fi

website/releases/archive_alpha.html

@@ -0,0 +1 @@
+../../archive/dist/archive.html

website/releases/classifier_alpha.html

@@ -0,0 +1 @@
+../../classifier/dist/classifier.html

website/releases/landing_alpha.html

@@ -0,0 +1 @@
+../../landing/dist/index.html

website/releases/mdedit_alpha.html

@@ -0,0 +1 @@
+../../mdedit/dist/mdedit.html

website/releases/transmittal_alpha.html

@@ -0,0 +1 @@
+../../transmittal/dist/transmittal.html