fix(cli): improve --output-schema help text with JSON Schema format details

Fixes bounty issue #1401

The --output-schema flag previously had a vague description 'JSON schema file
for structured output'. This change improves the help text to:
- Mention the JSON Schema format (draft-07 or later)
- Provide a concrete example of a valid schema
- Link to json-schema.org for full specification

Author: factorydroid

cortex-cli/src/main.rs

@@ -241,8 +241,23 @@ struct ExecCommand {
     #[arg(short, long, default_value = "human")]
     format: String,
 
-    /// JSON schema file for structured output
-    #[arg(long)]
+    /// JSON Schema file (draft-07+) defining the expected output structure.
+    /// See https://json-schema.org for format details
+    #[arg(
+        long,
+        value_name = "FILE",
+        long_help = "Path to a JSON Schema file (draft-07 or later) for structured output.\n\n\
+                     The schema defines the expected structure of the output. Example:\n\n\
+                     {\n  \
+                       \"type\": \"object\",\n  \
+                       \"properties\": {\n    \
+                         \"summary\": { \"type\": \"string\" },\n    \
+                         \"items\": { \"type\": \"array\", \"items\": { \"type\": \"string\" } }\n  \
+                       },\n  \
+                       \"required\": [\"summary\"]\n\
+                     }\n\n\
+                     See https://json-schema.org for the full JSON Schema specification."
+    )]
     output_schema: Option<PathBuf>,
 
     /// Additional writable directories