Replace nix hash tasks with Evergreen FOD refresh

README.md

@@ -123,8 +123,8 @@ dt nix:check
 After `pnpm-lock.yaml` changes:
 
 ```bash
-dt nix:hash:genie
-dt nix:hash
+refresh Nix FOD hashes for genie
+refresh all stale Nix FOD hashes with your repo workflow
 ```
 
 ## Quick Start

nix/devenv-modules/otel/dashboards/dt-duration-trends.jsonnet

@@ -14,7 +14,7 @@
 //   - lint:check (linting)
 //   - test:run (test execution)
 //   - mr:fetch-apply (repo synchronization)
-//   - nix:build, nix:check, nix:hash (Nix operations)
+//   - nix:build, nix:check (Nix operations)
 //   - tsc per-project breakdown (from extendedDiagnostics spans)
 local g = import 'g.libsonnet';
 local lib = import 'lib.libsonnet';
@@ -280,7 +280,6 @@ g.dashboard.new('dt Task Duration Trends')
   ),
 
   at(
-    taskDurationPanel('nix:hash:* (p50 / p95 / p99)', 'nix:hash:.*'),
     16, y.nixContent, 8, 8,
   ),
 

nix/devenv-modules/tasks/README.md

@@ -36,7 +36,7 @@ imports = [
     flaky "File not found" errors when pnpm is concurrently mutating/symlinking
     `node_modules` during CI.
 - `megarepo.nix` - Megarepo workspace tasks
-- `nix-cli.nix` - Nix CLI build tasks (nix:hash, nix:build, nix:flake:check)
+- `nix-cli.nix` - Nix CLI build/check tasks
 - `pnpm.nix` - pnpm install tasks
 - `setup.nix` - Setup tasks
 - `test.nix` - Test tasks