#45 issue list: labels/milestone columns + filter docs + field-preservation regression test

SOURCE: wr1te swarm #6+#8 + stale-binary audit (probed on current main): list --milestone filter EXISTS and works; per-verb help exists; the "label wipes milestone" bug does NOT reproduce (field preservation landed earlier). Their #2/#3/#8 were a stale install — the discoverability signal remains: FIX (a) human issue list table gains a labels column (+ milestone when set) — thin view of --json; (b) issue list --help const documents the four filters (--label --assignee --state --milestone); (c) REGRESSION TEST: label+assign an issue carrying milestone+labels+assignee -> ALL fields survive (the silent-wipe class stays dead). DONE: table shows labels; help lists filters; test pins preservation.