chore: untrack stray .claude/scheduled_tasks.lock and gitignore .claude/

A runtime scheduler lock was accidentally swept into the previous
commit by `git add -A`. Remove it from tracking (file stays on disk)
and ignore the whole `.claude/` dir so local agent runtime state never
lands in the repo again.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.claude/scheduled_tasks.lock

@@ -1 +0,0 @@
-{"sessionId":"a27586bb-2ca7-4e92-8d82-12f41b39f392","pid":3106893,"procStart":"59753850","acquiredAt":1780571089798}

.gitignore

@@ -7,3 +7,4 @@ cortex.toml
 models.toml
 doc/plan/*
 /target-cuda/
+.claude/