Content-hashed pkg assets (hash-files) so stale bundles can't pair with new wasm

An iPhone kept a heuristically-cached portal.js across three releases
(cached before Cache-Control: no-cache existed) and loaded it against
fresh wasm - its snippet imports 404'd, hydration never started, and
the gesture field never mounted. With hash-files = true every pkg
file is content-named and the freshly served page references exactly
its own bundle; hash.txt ships beside the binary (leptos resolves it
next to current_exe), the shell links the stylesheet through
HashedStylesheet, and instances set LEPTOS_HASH_FILES=true.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Cargo.toml

@@ -131,6 +131,12 @@ bin-default-features = false
 lib-features = ["hydrate"]
 lib-default-features = false
 lib-profile-release = "wasm-release"
+# Content-hashed pkg names (portal.<hash>.js/wasm/css) + hash.txt: a
+# freshly served page can never reference a stale cached bundle - an
+# iPhone kept a heuristically-cached portal.js across three releases
+# and paired it with new wasm, silently killing hydration. Runtime
+# needs LEPTOS_HASH_FILES=true (set in each content repo's deploy env).
+hash-files = true
 
 # cargo release <level> is how a portal version is cut: bump, commit,
 # tag v{{version}}, push. CI (publish.yml) reacts to the tag and