refactor(core,storage): deduplicate code patterns (TODO-014)

Extract PttCapability event construction helper in events.rs.
Extract ensure_dir() helper in chanora_storage. Add TODO(refactor)
annotations for patterns requiring shared crate or API changes.

crates/chanora_bridge/src/lib.rs

@@ -56,6 +56,10 @@ pub enum BridgeError {
     /// The caller submitted a malformed command DTO.
     #[error("invalid command: {0}")]
     InvalidCommand(String),
+    // TODO(refactor): DnsFailed and ServerRejected mirror ProtocolError variants
+    // in chanora_protocol. These cannot be unified without changing the public FFI
+    // API (flutter_rust_bridge generates Dart types from these). Revisit only if
+    // the bridge error types are being reworked.
     /// Hostname resolution failed. Distinct from `Connection` so the
     /// UI can show a meaningful "Server not found" message.
     #[error("dns: could not resolve '{host}': {reason}")]

crates/chanora_cache/src/lib.rs

@@ -16,6 +16,9 @@
 use std::path::{Path, PathBuf};
 
 /// Errors raised by the blob cache.
+// TODO(refactor): Io(String) variant is duplicated across chanora_cache,
+// chanora_storage, and chanora_diagnostics. Could use a shared error type
+// or derive From<std::io::Error> instead of manually wrapping.
 #[derive(Debug, thiserror::Error)]
 pub enum BlobCacheError {
     /// Filesystem I/O error.

crates/chanora_prefetch/src/lib.rs

@@ -194,6 +194,9 @@ impl ServerPrefetcher {
     }
 }
 
+// TODO(refactor): `normalize_host` duplicates `chanora_resolver::normalize_args`
+// host trimming. Both do `host.trim().to_lowercase()`. Could move to a shared
+// utility in chanora_protocol or a tiny chanora_common crate if more crates need it.
 fn normalize_host(host: &str) -> String {
     host.trim().to_lowercase()
 }

crates/chanora_state/src/lib.rs

@@ -187,6 +187,10 @@ fn normalize_snapshot(snapshot: ServerSnapshot) -> ServerSnapshot {
     }
 }
 
+// TODO(refactor): StateEvent and Delta have mirrored variants (e.g.
+// StateEvent::ChannelChanged/ChannelDeleted vs Delta::ChannelUpserted/ChannelRemoved).
+// A proc-macro or macro_rules could generate the Delta-from-StateEvent mapping, but
+// the manual match is currently clear and the types serve different roles (input vs output).
 /// A change to the server state that the bridge should publish to
 /// Flutter. Deltas are cheap to construct and carry only the
 /// information that changed.

crates/chanora_storage/src/lib.rs

@@ -79,6 +79,10 @@ pub enum StorageError {
     Crypto(String),
 }
 
+fn ensure_dir(dir: &Path) -> Result<(), StorageError> {
+    fs::create_dir_all(dir).map_err(|e| StorageError::Io(format!("mkdir {dir:?}: {e}")))
+}
+
 /// Audio-related per-identity settings persisted alongside the
 /// identity file as a small JSON blob (SDD-095 / SDD-096). These
 /// are *not* secrets; they sit beside the encrypted identity in
@@ -193,7 +197,7 @@ impl IdentityFileStore {
     /// the DEK on first use; subsequent uses reuse the existing DEK.
     pub fn new(dir: impl AsRef<Path>) -> Result<Self, StorageError> {
         let dir = dir.as_ref();
-        fs::create_dir_all(dir).map_err(|e| StorageError::Io(format!("mkdir {dir:?}: {e}")))?;
+        ensure_dir(dir)?;
         let canonical = fs::canonicalize(dir)
             .map(|p| p.to_string_lossy().into_owned())
             .unwrap_or_else(|_| dir.to_string_lossy().into_owned());
@@ -814,7 +818,7 @@ impl BookmarkRepository {
     }
 
     fn open(dir: &Path, crypto: Option<Box<dyn Crypto>>) -> Result<Self, StorageError> {
-        fs::create_dir_all(dir).map_err(|e| StorageError::Io(format!("mkdir {dir:?}: {e}")))?;
+        ensure_dir(dir)?;
         let path = dir.join("chanora.db");
         let conn = Connection::open(&path)
             .map_err(|e| StorageError::Sqlite(format!("open {path:?}: {e}")))?;