docs: correct two claims this repository makes that do not hold

README.md

@@ -355,8 +355,8 @@ Upgrading the fabric binary under a running daemon — especially on a remote
 machine reached only over `fabric shell` — must be done lockout-safe: a botched
 restart can sever the only path back to the box. Follow this order.
 
-Download a release asset directly, verify it against the release's combined
-`SHA256SUMS` manifest, and stage both the old and new binaries with same-directory
+Download a release asset directly, verify it against that asset's published
+`.sha256`, and stage both the old and new binaries with same-directory
 renames. A release archive contains exactly one member named literal `fabric`
 (not `./fabric`); verify that shape before extracting:
 
@@ -377,9 +377,12 @@ download_dir="$(mktemp -d)"
 trap 'rm -rf "$download_dir"' EXIT
 
 curl --fail --location "$release_url/$asset" --output "$download_dir/$asset"
-curl --fail --location "$release_url/SHA256SUMS" --output "$download_dir/SHA256SUMS"
+curl --fail --location "$release_url/$asset.sha256" --output "$download_dir/$asset.sha256"
 
-expected="$(awk -v asset="$asset" '$2 == asset { print $1 }' "$download_dir/SHA256SUMS")"
+# The release publishes ONE .sha256 per asset, not a combined manifest. The file
+# holds "<hash>  dist/<archive>", with the builder's path still in it, so
+# `shasum -c` fails here. Take field one and compare it ourselves.
+expected="$(awk 'NR == 1 { print $1 }' "$download_dir/$asset.sha256")"
 test -n "$expected"
 if command -v sha256sum >/dev/null 2>&1; then
   actual="$(sha256sum "$download_dir/$asset" | awk '{ print $1 }')"

src/sync/manifest.rs

@@ -56,8 +56,24 @@ pub struct FileMeta {
     pub hash: ContentHash,
     /// File size in bytes (informational; the hash is the identity).
     pub size: u64,
-    /// Whether the file is executable, the way git tracks it: a file is either
-    /// mode 644 or 755, and no other permission bit is replicated.
+    /// Whether the file is executable, the way git tracks it. ONLY this bit
+    /// replicates; no other permission bit crosses.
+    ///
+    /// The resulting MODE is not fixed, and an earlier version of this comment
+    /// claimed it was. Materialization creates the file with `fs::write`, which
+    /// yields `0666 & ~umask`, and then ORs in `0o111`. So the mode depends on
+    /// the RECEIVING host's umask:
+    ///
+    /// | receiver umask | plain file | executable file |
+    /// | --- | --- | --- |
+    /// | 022 | 0644 | 0755 |
+    /// | 002 | 0664 | 0775 |
+    ///
+    /// Observed on hetz and droppy on 2026-08-23: 0664 and 0775, both umask
+    /// 002. Do NOT depend on an exact mode here; depend only on the executable
+    /// bit. st2's render deliberately differs: it writes an exact mode that is
+    /// immune to umask, so the two systems do not agree on the other bits and
+    /// are not meant to.
     ///
     /// Defaulted so a peer that predates this field still parses. Note the
     /// asymmetry: adding a field with a default is safe, removing one is not.