fix(#2748): pass browserProvider into skill() discovery

skill-context already filtered browser-related skills using the configured
browser provider, but the skill tool rebuilt discovery without forwarding
browserProvider. That caused skills like agent-browser to be prompt-visible
while skill() could still fail to resolve them unless browser_automation_engine.provider
was explicitly threaded through both paths.

Fix:
- pass skillContext.browserProvider from tool-registry into createSkillTool
- extend SkillLoadOptions with browserProvider
- forward browserProvider to getAllSkills()
- add regression tests for execution and description visibility

src/tools/skill/tools.ts

@@ -189,7 +189,7 @@ export function createSkillTool(options: SkillLoadOptions = {}): ToolDefinition
 
   const getSkills = async (): Promise<LoadedSkill[]> => {
     clearSkillCache()
-    const discovered = await getAllSkills({disabledSkills: options?.disabledSkills})
+    const discovered = await getAllSkills({disabledSkills: options?.disabledSkills, browserProvider: options?.browserProvider})
     const allSkills = !options.skills
       ? discovered
       : [...discovered, ...options.skills.filter(s => !new Set(discovered.map(d => d.name)).has(s.name))]