fix: ls tracking baseline should compare against `ls` not `ls -la`

Problem

rtk ls internally runs ls -la to get file metadata for grouping/filtering, then compresses the output. The savings % is tracked against the ls -la output, not plain ls (which is what the agent would have run without RTK).

This inflates the reported savings. Example from user report:

• ls = 332 tokens
• ls -la = 4173 tokens
• rtk ls = 993 tokens
• Reported: 76.2% savings (vs ls -la)
• Actual: -199% vs plain ls

Fix

Track against the baseline command the agent would have run (ls), not the internal enriched command (ls -la).

In src/ls.rs line 113-118, change the tracking input from the ls -la raw output to a plain ls capture (or estimate).

Reference

https://www.reddit.com/r/ClaudeAI/comments/1rjkf9r/comment/oa3trnn/

Start in src/ls.rs around lines 113-118, where tracking uses the raw output from the internal ls -la command. Change the tracking baseline to represent plain ls, either through a capture or an estimate. Done means the reported savings compares rtk ls with the command an agent would normally run, rather than ls -la.