site: layout width tiers + masonry glide — column changes animate instead of snapping

Named width tiers (mobile/narrow/regular/wide) with body max-width easing
between them; grid pages opt in via BaseLayout `wide`. Masonry is now
absolute-positioned with FLIP glides on column-count changes: targets are
computed from the *final* container width (reading --max, which flips
instantly while max-width tweens), mid-glide column changes retarget
instead of being dropped, and container height eases so content below
rides along.

Claude-Session: https://claude.ai/code/session_01ADR9r5rw5NuvvnCxfYbMuc

.claude/scheduled_tasks.lock

@@ -1 +1 @@
-{"sessionId":"87abedef-67c7-43ce-984d-6586f084558f","pid":85715,"procStart":"Sun May  3 13:48:07 2026","acquiredAt":1777883275428}
+{"sessionId":"f84073a4-0271-4bee-83d1-e6095f6a42e0","pid":80707,"procStart":"Fri Jul  3 18:24:10 2026","acquiredAt":1783106632209}