Round-1 review fixes:
- Implement the auto-close path the header and issue body promised but did not
do: triage now records the REGRESSION case set and closes any open
[flake-triage] issue whose case is no longer regressing across the window, so
a fixed regression does not leave its tracker open forever (previously a false
written promise to maintainers).
- Anchor the JUnit name extraction on a leading space so a classname="..."
attribute preceding name="..." cannot be captured instead of the case name.
- Key issue idempotency on the title prefix + backtick-quoted case name rather
than a GitHub full-text search for an HTML-comment marker (search tokenizes
punctuation away, so the marker search could miss and open duplicates).
- Frame the per-attempt artifact union honestly as a best-effort enhancement:
the robust core signal is the streak across separate main run ids, which
stands on its own if only the latest attempt's artifact survives.
- Drop a dead awk array in the attempt-merge step.
Signed-off-by: IvanHunters <xorokhotnikov@gmail.com>