Clarify keyword rules in prompt and docs

Author: ngirard

README.md

@@ -130,7 +130,7 @@ taskgist "Create a new user authentication system with email verification and pa
 ```
 Example output:
 ```
-create-user-authentication-email-verification
+create-user-authentication-email-verification-password-reset
 ```
 
 **Using a file input:**

src/taskgist/baml_src/keywords.baml

@@ -13,6 +13,7 @@ function ExtractKeywords(taskDescription: string) -> KeywordPhrase {
     - Omit articles (the, a, an), common prepositions (in, on, to, for), and pronouns (it, this, that, etc.).
     - Be representative of the core task.
     - Not exceed 5 words
+    - Each returned word must be a single token with no spaces
 
     {{ ctx.output_format }}