fix(ci): Phase-2 fleet submission must not fail the security gate (#20)

Layer-1 propagation of hyperpolymath/hypatia#252. This repo's own copy
of hypatia-scan.yml hard-failed (exit 127) for any commit with >=1
finding: the "Submit findings to gitbot-fleet (Phase 2)" step cloned
gitbot-fleet and exec'd scripts/submit-finding.sh, which no longer
exists on gitbot-fleet's default branch.

Phase 2 is the collaborative LEARNING side-channel, not the security
gate. Fix: continue-on-error + self-healing body (non-fatal clone,
probe known script paths, graceful ::warning:: skip). Security
enforcement (the baseline-aware critical/high step) is unchanged.

Refs hyperpolymath/hypatia#252

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath