v0.8.1 — Usage tracker fix

Fixed

• Usage tracker (track-usage.sh) silently logged every invocation as "unknown" — it read tool name/input from env vars (CLAUDE_TOOL_NAME/CLAUDE_TOOL_INPUT) that Claude Code never sets. The PostToolUse hook payload actually arrives as JSON on stdin. Rewrote the script to parse stdin directly, with atomic file-locked writes and errors routed to ~/.moltbloat/errors.log instead of failing silently.

This had been degrading /moltbloat:usage data since the hook was introduced.

Full Changelog: v0.8.0...v0.8.1