fix: observation parsing and permalink limits (#446)

1. Hashtag detection now checks for standalone words starting with #
   instead of just checking if # appears anywhere in content.
   This prevents HTML color codes like #4285F4 from being
   interpreted as hashtags.

2. Observation permalinks now truncate content to 200 chars
   to stay under PostgreSQL's btree index limit of 2704 bytes.

Added tests for both fixes.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
Signed-off-by: phernandez <paul@basicmachines.co>

src/basic_memory/markdown/plugins.py

@@ -30,7 +30,9 @@ def is_observation(token: Token) -> bool:
 
     # Check for proper observation format: [category] content
     match = re.match(r"^\[([^\[\]()]+)\]\s+(.+)", content)
-    has_tags = "#" in content
+    # Check for standalone hashtags (words starting with #)
+    # This excludes # in HTML attributes like color="#4285F4"
+    has_tags = any(part.startswith('#') for part in content.split())
     return bool(match) or has_tags
 
 

src/basic_memory/models/knowledge.py

@@ -162,9 +162,14 @@ class Observation(Base):
 
         We can construct these because observations are always defined in
         and owned by a single entity.
+
+        Content is truncated to 200 chars to stay under PostgreSQL's
+        btree index limit of 2704 bytes.
         """
+        # Truncate content to avoid exceeding PostgreSQL's btree index limit
+        content_for_permalink = self.content[:200] if len(self.content) > 200 else self.content
         return generate_permalink(
-            f"{self.entity.permalink}/observations/{self.category}/{self.content}"
+            f"{self.entity.permalink}/observations/{self.category}/{content_for_permalink}"
         )
 
     def __repr__(self) -> str:  # pragma: no cover