chore(.gitignore): housekeeping — build_cpu/, blog/, scheduled_tasks.lock

Addresses the "trivial housekeeping" item flagged in .claude/state.md:
three untracked directories/files accumulated across recent sessions were
polluting every `git status` with no reason to be committed. Now ignored
at the top-level entries:

  build_cpu/                          — parallel CPU-only cmake dir
  blog/                               — local blog drafts (separate repo)
  .claude/scheduled_tasks.lock        — /loop runtime state

Post-commit `git status` is now clean (no untracked files).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: unamedkr

.gitignore

@@ -64,14 +64,19 @@ docs/assets/hero_backup.png
 build_nomt/
 build_nometal/
 build_metal/
+build_cpu/
 
 .env
 
 
 blog/build_cpu/
+blog/
 
 # Pillar 1 (Qwen3 coherence debugging)
 tools/pillar1/venv/
+
+# Claude Code scheduled-task lockfile (runtime state)
+.claude/scheduled_tasks.lock
 tools/pillar1/*.npz
 tools/pillar1/__pycache__/