test: strengthen safety-critical coverage

docs/COVERAGE_POLICY.md

@@ -0,0 +1,20 @@
+# Coverage policy
+
+ForgeFlow treats coverage as release evidence, not as a target to game. `npm run coverage`
+enforces 75% statements, 75% lines, 75% functions and 60% branches globally.
+
+The July 2026 hardening pass raised the measured baseline from 69.74% statements/lines,
+68.82% functions and 55.38% branches to at least 78% statements/lines, 79% functions and
+60% branches. The requested 65% global branch target was investigated but is not used as
+the release gate yet. Node/V8 discovers additional branch counters when previously
+unexecuted functions become covered; the denominator grew from 2,537 to more than 3,100
+while the new tests added hundreds of asserted branches. Raising the number by excluding
+command builders, platform guards or error adapters would make the result look better
+without increasing deployment safety.
+
+The 60% global gate is therefore paired with scenario-level evidence for the critical
+boundaries: deploy-key rollback, deployment verification, Gitea authentication and
+redirects, SSH host identity and output limits, inventory reconciliation, stale plans,
+configuration recovery, release integrity and updater failure modes. New code must not
+reduce the global baseline. A future increase to 65% should come from additional asserted
+failure scenarios, not ignore comments or source exclusions.