feat(skills): enhance skills system with matching and evaluation

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/app/agents/skills/matcher.py

@@ -0,0 +1,32 @@
+from __future__ import annotations
+
+import re
+
+
+def extract_match_terms(text: str | None) -> list[str]:
+    source = (text or "").lower()
+    terms = [token for token in re.findall(r"[a-z0-9_]+", source) if len(token) >= 3]
+
+    for chunk in re.findall(r"[\u4e00-\u9fff]+", text or ""):
+        if len(chunk) >= 2:
+            terms.append(chunk)
+            if len(chunk) > 4:
+                for index in range(len(chunk) - 1):
+                    terms.append(chunk[index : index + 2])
+
+    return list(dict.fromkeys(terms))
+
+
+def score_text_match(query_text: str, *corpus_parts: str | None) -> tuple[float, list[str]]:
+    query_terms = extract_match_terms(query_text)
+    if not query_terms:
+        return 0.0, []
+
+    corpus = " ".join(part for part in corpus_parts if part).lower()
+    matched_terms = [term for term in query_terms if term and term in corpus]
+    if not matched_terms:
+        return 0.0, []
+
+    coverage = len(matched_terms) / max(len(query_terms), 1)
+    density = min(len(matched_terms), 4) / 4
+    return round(min(1.0, coverage * 0.7 + density * 0.3), 3), matched_terms