refactor: Remove hardcoded Web Research section from system prompt

- Web Research instructions now come from skills/research/SKILL.md
- Skills are dynamically loaded and injected via generate_skills_prompt()
- Remove test_both_prompts_have_web_research test (no longer applicable)
- Remove unused G3Status::research_complete() function

This completes the externalization of research as a skill.

crates/g3-cli/src/g3_status.rs

@@ -274,23 +274,6 @@ impl G3Status {
         Self::done();
     }
 
-    /// Print research completion notification: "g3: N research report(s) ... [done/failed]"
-    ///
-    /// Used for real-time notification when background research completes.
-    pub fn research_complete(count: usize, all_succeeded: bool) {
-        let report_word = if count == 1 { "report" } else { "reports" };
-        print!(
-            "{} {} research {} ...",
-            Self::format_prefix(),
-            count,
-            report_word
-        );
-        if all_succeeded {
-            Self::done();
-        } else {
-            Self::failed();
-        }
-    }
 }
 
 #[cfg(test)]