fix: use field-specific bozo_exception messages and fix read_text_str docs

Use distinct bozo_exception messages per field (channel title, channel
description, feed id) instead of generic message. Fix read_text_str doc
comment to accurately reflect usage at entry-level call sites where
bozo propagation is not yet implemented.

Author: bug-ops

crates/feedparser-rs-core/src/parser/atom.rs

@@ -157,7 +157,7 @@ fn parse_feed_element(
                         if bozo {
                             feed.bozo = true;
                             feed.bozo_exception =
-                                Some("Unresolvable entity in feed content".to_string());
+                                Some("Unresolvable entity in feed id".to_string());
                         }
                         feed.feed.id = Some(text);
                     }

crates/feedparser-rs-core/src/parser/common.rs

@@ -474,9 +474,9 @@ pub fn skip_element(
 
 /// Read text content, discarding the bozo signal.
 ///
-/// Use this at call sites where `feed` is not in scope and bozo propagation
-/// is handled by a higher-level caller, or where the text field is metadata
-/// that does not carry entity content from untrusted feeds.
+/// Use this at call sites where `ParsedFeed` is not in scope and bozo
+/// propagation to the feed level is not yet implemented, such as entry-level
+/// fields (title, summary, content, author, etc.). See #70.
 #[inline]
 pub fn read_text_str(
     reader: &mut Reader<&[u8]>,

crates/feedparser-rs-core/src/parser/rss.rs

@@ -343,7 +343,8 @@ fn parse_channel_standard(
             let (text, bozo) = read_text(reader, buf, limits)?;
             if bozo {
                 feed.bozo = true;
-                feed.bozo_exception = Some("Unresolvable entity in feed content".to_string());
+                feed.bozo_exception =
+                    Some("Unresolvable entity in channel title".to_string());
             }
             feed.feed.set_title(TextConstruct {
                 value: text,
@@ -365,7 +366,8 @@ fn parse_channel_standard(
             let (text, bozo) = read_text(reader, buf, limits)?;
             if bozo {
                 feed.bozo = true;
-                feed.bozo_exception = Some("Unresolvable entity in feed content".to_string());
+                feed.bozo_exception =
+                    Some("Unresolvable entity in channel description".to_string());
             }
             feed.feed.set_subtitle(TextConstruct {
                 value: text,