The opaque content type is one core constant: local::OPAQUE_MIME

"application/octet-stream" was written out in the blob server, its test, the
store's normalize_mime and the wire default. All four now read OPAQUE_MIME; the
schema's SQL column default names the same string and says so.

DRY pass #2, batch 2, F7 (#5372).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

core/src/local/mod.rs

@@ -24,6 +24,11 @@ pub const DB_FILE: &str = "inkwell.db";
 /// Attachment bytes, filed by content hash, beside [`DB_FILE`].
 pub const BLOBS_DIR: &str = "blobs";
 
+/// The type of bytes whose type isn't known, or isn't safe to say: stored for an
+/// attachment that declared none, and served for one that can't be shown inline.
+/// The schema's column default (`schema.rs`) is the same string, in SQL.
+pub const OPAQUE_MIME: &str = "application/octet-stream";
+
 /// An instant in the store's own form: RFC 3339, UTC, milliseconds, `Z`. Every
 /// stored time is written this way, which is what makes lexical order chronological.
 pub fn iso(t: DateTime<Utc>) -> String {

core/src/local/store.rs

@@ -15,7 +15,7 @@ use uuid::Uuid;
 use crate::local::derive;
 use crate::local::models::*;
 use crate::local::recur;
-use crate::local::{iso, now};
+use crate::local::{iso, now, OPAQUE_MIME};
 
 fn new_id() -> String {
     Uuid::new_v4().to_string()
@@ -792,7 +792,7 @@ fn normalize_mime(raw: &str) -> String {
         .trim()
         .to_ascii_lowercase();
     if bare.is_empty() {
-        "application/octet-stream".to_string()
+        OPAQUE_MIME.to_string()
     } else {
         bare
     }

core/src/sync/blobs.rs

@@ -12,6 +12,8 @@ use std::fs;
 use std::path::{Path, PathBuf};
 use std::sync::OnceLock;
 
+use crate::local::OPAQUE_MIME;
+
 /// A sha256 in lowercase hex, and nothing else.
 ///
 /// This is a **path-safety** check, not a formatting nicety: the hash is taken
@@ -189,7 +191,7 @@ fn content_type_for(mime: &str) -> String {
     if familiar && printable {
         mime.to_string()
     } else {
-        "application/octet-stream".to_string()
+        OPAQUE_MIME.to_string()
     }
 }
 
@@ -306,7 +308,7 @@ mod tests {
     fn a_scriptable_type_is_served_as_a_download() {
         // This scheme is an origin of its own. An attachment claiming to be HTML
         // must not be handed back as a document that can run there.
-        let opaque = "application/octet-stream";
+        let opaque = OPAQUE_MIME;
         assert_eq!(content_type_for("text/html"), opaque);
         assert_eq!(content_type_for("application/javascript"), opaque);
         // An image family member that is really a document with script in it.

core/src/sync/wire.rs

@@ -8,6 +8,8 @@
 
 use serde::Deserialize;
 
+use crate::local::OPAQUE_MIME;
+
 #[derive(Debug, Clone, Deserialize, Default)]
 pub struct ChangesPage {
     #[serde(default)]
@@ -161,5 +163,5 @@ fn default_color() -> String {
 }
 
 fn default_mime() -> String {
-    "application/octet-stream".to_string()
+    OPAQUE_MIME.to_string()
 }