feat(html): adoption-style hydration with mismatch reporting

hydrate(oldNode, newNode) normalizes the client tree to parser text-node
granularity, walks both trees to report the first server/client markup
disagreement (node, text, attribute, or child count, with a path), then
morphs — matching nodes are adopted in place, the client render wins.
choo.mount() now hydrates and console.warns on mismatch.

Building this surfaced two real isomorphism divergences, both fixed:
adjacent text nodes from template holes vs the parser's merged runs
(folded via Node.normalize), and the server serializing onclick="" where
the browser sets a property — event handlers now leave no trace in server
markup at all.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014NgfSjHE11oFpoSnLVKLXd

packages/core/index.js

@@ -2,6 +2,7 @@
 // Same API, same event flow; ESM, consolidated nano* internals in ./lib.
 
 import morph from '@choojs/html/morph'
+import hydrate from '@choojs/html/hydrate'
 import nanotiming from './lib/timing.js'
 import Nanorouter from './lib/router.js'
 import Nanobus from './lib/bus.js'
@@ -213,8 +214,20 @@ export class Choo {
         self._tree.nodeName.toLowerCase() + '> is not the same type as the new node <' +
         newTree.nodeName.toLowerCase() + '>.')
 
+      // First render adopts the existing (usually server-rendered) DOM:
+      // matching nodes are left in place, and any server/client markup
+      // disagreement is reported before the client render wins.
       const morphTiming = nanotiming('choo.morph')
-      morph(self._tree, newTree)
+      hydrate(self._tree, newTree, {
+        onMismatch: function (diff) {
+          console.warn(
+            'choo.mount: server and client markup differ at ' + diff.path +
+            ' (' + diff.reason + '): server rendered ' + diff.server +
+            ', client rendered ' + diff.client +
+            '. The client version wins; fix the view so both sides agree.'
+          )
+        }
+      })
       morphTiming()
 
       renderTiming()