another step

server/CONVENTIONS.md

@@ -94,6 +94,32 @@ List<string> tags = ["new", "sale"];
 
 No abbreviations unless universally understood (`dto`, `id`, `url`). No Hungarian notation (`strName`, `intCount`).
 
+### No unused code
+
+Leave nothing dead behind. Remove unused `using` directives, local variables, parameters, private fields, and private members rather than letting them accumulate.
+
+- These already surface as compiler/analyzer signals — `CS0168` (variable declared, never used), `CS0219` (variable assigned, value never used), `CS0169` (private field never used), `IDE0005` (unnecessary `using`). The quality gate is **zero new warnings**, so treat unused code as a gate failure.
+- **Delete it — don't silence it.** Do not add `#pragma warning disable`, throwaway discards, or `_ =` assignments just to quiet the analyzer.
+- The one exception: a parameter that must exist to satisfy an interface or delegate signature but is genuinely unused. Keep it, name it conventionally, and add a one-line `// why` only if the reason isn't obvious.
+
+### Comments — explain *why*, never *what*
+
+Code that needs a comment to be understood usually needs a better name instead. Prefer self-documenting names over prose.
+
+- **Do not** write comments that restate what the code already says — no `// constructor`, `// loop over users`, or XML-doc that merely echoes the method name.
+- **Do** add a comment only where a non-obvious decision, constraint, business rule, workaround, or trade-off is *not* evident from the code — explain the reasoning, not the mechanics.
+- Keep any necessary comment tight, and delete comments that no longer match the code.
+
+```csharp
+// ❌ restates the obvious
+// increment the retry counter
+retryCount++;
+
+// ✅ captures a non-obvious constraint the code can't express on its own
+// Payment gateway rejects amounts above 50M IRR per call; split larger settlements upstream.
+if (amount > MaxPerCallRial) ...
+```
+
 ---
 
 ## 3. Async / await