chore(prompts): clarify linked SKILL.md file handling (#10907)

src/core/prompts/sections/skills.ts

@@ -80,6 +80,16 @@ CONSTRAINTS:
 - FAILURE to perform this check is an error.
 </mandatory_skill_check>
 
+<linked_file_handling>
+- When a SKILL.md is loaded, ONLY the contents of SKILL.md are present.
+- Files linked from SKILL.md are NOT loaded automatically.
+- The model MUST explicitly decide to read a linked file based on task relevance.
+- Do NOT assume the contents of linked files unless they have been explicitly read.
+- Prefer reading the minimum necessary linked file.
+- Avoid reading multiple linked files unless required.
+- Treat linked files as progressive disclosure, not mandatory context.
+</linked_file_handling>
+
 <context_notes>
 - The skill list is already filtered for the current mode: "${currentMode}".
 - Mode-specific skills may come from skills-${currentMode}/ with project-level overrides taking precedence over global skills.