What does this PR do?
LockFile.save() and TapsManager.save() write lock.json and taps.json using write_text(), which is non-atomic. If the process is killed or crashes mid-write (e.g. OOM, SIGKILL, power loss), the target file is left partially written and JSON-corrupt. On the next run load() falls back to an empty default — silently discarding all installed-skill records or all custom taps.

Switches both methods to atomic_json_write from utils, which writes to a temp file, fsyncs, then os.replaces — guaranteeing the old file survives intact if the write doesn't complete.

Type of Change

• Bug fix

Changes Made

• tools/skills_hub.py: replace write_text with atomic_json_write in LockFile.save() and TapsManager.save()

How to Test

1. Add a skill tap: hermes skills hub tap some/repo
2. Kill -9 the process during the write
3. Confirm taps.json is not corrupted on next read
4. Same for hermes skills install → kill → re-run hermes skills list

Checklist

• Read the Contributing Guide
• Commit messages follow Conventional Commits
• Searched for existing PRs to avoid duplicates
• PR contains only changes related to this fix
• Tested on: Ubuntu 24.04 (WSL2)
• No documentation changes needed