fix: skill discovery path doubling and pattern/name matching

Three related bugs that prevent agent skills from loading:

1. **Doubled "skills/" prefix in discovery** (skills-adapter.ts)
   `discoverSkills()` unconditionally prepends "skills/" to the relative
   path, but `baseDir` points to the parent of the skills directory
   (e.g. `~/.fusion/agent`), so `relative()` already returns a path
   starting with "skills/". Result: IDs like
   `auto::skills/skills/web-research/SKILL.md` instead of
   `auto::skills/web-research/SKILL.md`.

   Fix: only prepend "skills/" when the relative path does not already
   start with it.

2. **normalizeAgentSkills does not extract name from full ID**
   (session-skill-context.ts)
   The dashboard saves full skill IDs (e.g.
   `"auto::skills/web-research/SKILL.md"`) into agent
   `metadata.skills`. The runtime matches these against
   `skill.name` (e.g. `"web-research/SKILL.md"`) — they never match,
   so agent skills silently fail to load.

   Fix: when an entry contains "::", parse out the skill name (last
   two path segments) before matching.

3. **Pattern matching uses absolute filePath instead of skill name**
   (skill-resolver.ts)
   Settings patterns written by `toggleExecutionSkill()` are relative
   (e.g. `"web-research/SKILL.md"`), but the resolver compares them
   against `skill.filePath` which is absolute. Patterns can never
   match, producing spurious "not found in discovered skills" warnings.

   Fix: match patterns against `skill.name` (case-insensitive) with
   fallback to exact `skill.filePath` match for backward compatibility.

packages/engine/src/session-skill-context.ts

@@ -101,10 +101,22 @@ export function normalizeAgentSkills(
       }
     }
 
-    // Skip invalid/empty entries and deduplicate
-    if (name && name.length > 0 && !seen.has(name)) {
-      seen.add(name);
-      result.push(name);
+    // Skip invalid/empty entries and deduplicate.
+    // If the entry is a full skill ID ("source::path"), extract just the
+    // skill name (last two path segments) so it matches the discovered
+    // skill.name produced by extractSkillName().
+    if (name && name.length > 0) {
+      if (name.includes("::")) {
+        const idPath = name.split("::").pop()!;
+        const parts = idPath.replace(/\\/g, "/").split("/").filter(Boolean);
+        if (parts.length >= 2) {
+          name = parts.slice(-2).join("/");
+        }
+      }
+      if (!seen.has(name)) {
+        seen.add(name);
+        result.push(name);
+      }
     }
   }