fix: skill supporting-file listings no longer repeat the absolute path per line

The supporting-files block emitted every file twice per line
(relative  ->  absolute), duplicating an identical directory prefix
hundreds of times on reference-heavy skills. The absolute base is
already stated once in the [Skill directory: ...] header and the
footer example, so each line now carries only the relative path.

On hermes-agent-dev (462 supporting files) the activation message
drops from 42,145 to 29,042 o200k tokens (-13,103, -31%) — paid on
every session that preloads or invokes the skill.

agent/skill_commands.py

@@ -391,9 +391,12 @@ def _build_skill_message(
             # Skill is from an external dir — use the skill name instead
             skill_view_target = skill_dir.name
         parts.append("")
-        parts.append("[This skill has supporting files:]")
+        parts.append(
+            "[This skill has supporting files (paths relative to the skill "
+            "directory above):]"
+        )
         for sf in supporting:
-            parts.append(f"- {sf}  ->  {skill_dir / sf}")
+            parts.append(f"- {sf}")
         parts.append(
             f'\nLoad any of these with skill_view(name="{skill_view_target}", '
             f'file_path="<path>"), or run scripts directly by absolute path '

tests/agent/test_skill_commands.py

@@ -691,7 +691,7 @@ class TestSkillDirectoryHeader:
         assert f"[Skill directory: {skill_dir}]" in msg
         assert "Resolve any relative paths" in msg
 
-    def test_supporting_files_shown_with_absolute_paths(self, tmp_path):
+    def test_supporting_files_listed_relative_only(self, tmp_path):
         with patch("tools.skills_tool.SKILLS_DIR", tmp_path):
             skill_dir = _make_skill(tmp_path, "scripted-skill")
             (skill_dir / "scripts").mkdir()
@@ -700,11 +700,17 @@ class TestSkillDirectoryHeader:
             msg = build_skill_invocation_message("/scripted-skill")
 
         assert msg is not None
-        # The supporting-files block must emit both the relative form (so the
-        # agent can call skill_view on it) and the absolute form (so it can
-        # run the script directly via terminal).
-        assert "scripts/run.js" in msg
-        assert str(skill_dir / "scripts" / "run.js") in msg
+        # Each supporting file is listed ONCE, as a relative path. Repeating
+        # the absolute skill-dir prefix per line cost ~9K tokens on skills
+        # with hundreds of references; the absolute base is already stated
+        # once in the [Skill directory: ...] header and the footer example.
+        assert "- scripts/run.js" in msg
+        assert f"- scripts/run.js  ->  " not in msg
+        assert str(skill_dir / "scripts" / "run.js") not in msg.split(
+            "[This skill has supporting files"
+        )[1].split("\nLoad any of these")[0]
+        # Absolute resolution stays available via the header + footer example.
+        assert f"[Skill directory: {skill_dir}]" in msg
         assert f"node {skill_dir}/scripts/foo.js" in msg