feat(segkit): add ci wrap and ci summary subcommands

Adds `segkit ci wrap -- <command>` to run commands with timing/exit/stderr
capture to JSONL reports, and `segkit ci summary` to generate markdown
tables from those artifacts for $GITHUB_STEP_SUMMARY.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: abueide

segkit/Cargo.lock

@@ -21,3 +21,4 @@ which = "7"
 [dev-dependencies]
 assert_cmd = "2"
 predicates = "3"
+tempfile = "3"