refactor: fix flaky test and remove dead code in recent commits

Fixes issues in the last 11 commits:

1. pending_research.rs: Fix flaky test_generate_id_uniqueness
   - Replaced random u16 suffix with atomic counter for guaranteed uniqueness
   - The timestamp+random approach could collide when generating IDs rapidly
   - Now uses static AtomicU32 counter that increments monotonically

2. embedded/adapters/glm.rs: Remove unused in_code_fence field
   - Field was written but never read (dead code)
   - Removed from struct definition, constructor, and reset()

3. embedded/adapters/glm.rs: Fix orphaned tests
   - Two tests (test_strip_code_fences, test_code_fenced_tool_call) were
     outside the #[cfg(test)] mod tests block
   - Moved closing brace to include them in the test module

All 446 library tests pass.

Agent: fowler

crates/g3-core/src/pending_research.rs

@@ -139,12 +139,15 @@ impl PendingResearchManager {
     /// Generate a unique research ID
     pub fn generate_id() -> ResearchId {
         use std::time::{SystemTime, UNIX_EPOCH};
+        use std::sync::atomic::{AtomicU32, Ordering};
+        static COUNTER: AtomicU32 = AtomicU32::new(0);
+        
         let timestamp = SystemTime::now()
             .duration_since(UNIX_EPOCH)
             .unwrap()
             .as_millis();
-        // Use timestamp + random suffix for uniqueness
-        format!("research_{:x}_{:04x}", timestamp, rand::random::<u16>())
+        let counter = COUNTER.fetch_add(1, Ordering::Relaxed);
+        format!("research_{:x}_{:08x}", timestamp, counter)
     }
 
     /// Register a new research task