fix(telemetry): avoid low savings arg leakage

[YOMXXX]

Summary

• report only coarse command labels for telemetry command stats
• stop low_savings_commands from sending URL/path/token-like command arguments
• cover rtk proxy and rtk:toml command forms with an in-memory tracking regression test

Fixes #1785

Verification

• cargo +1.93.0 fmt --check
• git diff --check
• cargo +1.93.0 test tracking::tests -- --nocapture
• cargo +1.93.0 test telemetry -- --nocapture
• cargo +1.93.0 clippy --all-targets
• cargo +1.93.0 test --all -- --skip small_grep_not_worse_than_plain