chore: stop tracking local tix state

[sedge-bot]

Summary

• Removes the committed .tix task-tracker store from the repo
• Adds .tix/ to .gitignore so local agent/task-tracker state stays local

Verification

• git diff --cached --stat before commit showed only .gitignore plus .tix removals
• git status --short was clean before push

[vercel]

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[sedge-bot]

Closing as obsolete: current main already includes the local task-tracking cleanup (.tix/ ignored and tracked .tix files removed), so this PR no longer has unique delivery work to merge.