Add file reference guidelines to gpt-5 prompt (#3651)

codex-rs/core/prompt.md

@@ -251,6 +251,16 @@ You are producing plain text that will later be styled by the CLI. Follow these
 - Apply to inline examples and to bullet keywords if the keyword itself is a literal file/command.
 - Never mix monospace and bold markers; choose one based on whether it’s a keyword (`**`) or inline code/path (`` ` ``).
 
+**File References**
+When referencing files in your response, make sure to include the relevant start line and always follow the below rules:
+  * Use inline code to make file paths clickable.
+  * Each reference should have a stand alone path. Even if it's the same file.
+  * Accepted: absolute, workspace‑relative, a/ or b/ diff prefixes, or bare filename/suffix.
+  * Line/column (1‑based, optional): :line[:column] or #Lline[Ccolumn] (column defaults to 1).
+  * Do not use URIs like file://, vscode://, or https://.
+  * Do not provide range of lines
+  * Examples: src/app.ts, src/app.ts:42, b/server/index.js#L10, C:\repo\project\main.rs:12:5
+
 **Structure**
 
 - Place related bullets together; don’t mix unrelated concepts in the same section.