test: triage 37 skipped-test sites — closure comments pinning rationale (Q-1)

Closes Q-1 (cat-s3-58ce7e9840be) — 37 t.Skip / testing.Short() sites
across 9 test files audited. Per-site verdict matrix:

  - cmd/agent/verify_test.go (1 site): defensive guard against unreachable
    httptest.NewTLSServer code path. Document-skip with closure comment.

  - deploy/test/qa_test.go (11 sites): file already gated by `//go:build qa`
    tag. The 11 t.Skip("Requires X — manual test") markers are runtime
    second-line guards for operators who run -tags qa against a stack
    missing the required external service. File-level header comment
    block added explaining the manual-test convention.

  - deploy/test/healthcheck_test.go (5 sites): 3 docker-availability +
    1 testing.Short + 1 hard-skip for not-yet-wired runtime probe
    (image-spec contract above already covers the audit-flagged
    regression). All correctly gated; file-level header comment block
    added explaining each.

  - deploy/test/integration_test.go (5 sites): in-flight-state guards
    (poll-with-skip after 90s polling for agent-online, inter-test
    Phase04→Phase07 ordering, scheduler-tick race for discovered certs,
    inter-test issuer fallthrough, defensive PEM-empty assertion).
    Each site now has a closure comment explaining why skip is the
    right choice rather than fail (upstream phase already surfaces the
    real failure; skipping prevents masking root cause behind cascading
    noise).

  - internal/repository/postgres/{testutil,seed,repo}_test.go (5 sites):
    testing.Short() gates for testcontainers-backed live PostgreSQL
    integration tests. All correctly gated; closure comments added
    naming the run command.

  - internal/connector/notifier/email/email_test.go (2 sites):
    anti-fixture assertions (test asserts SMTP dial fails; if a captive
    portal black-holes the call to success, skip rather than false-pass).
    Closure comments added explaining the fixture assumption.

  - internal/connector/target/iis/iis_test.go (2 sites): platform-gated
    skip for powershell.exe absence on non-Windows hosts. Mirrors the
    production iis_connector.go LookPath guard. Closure comments added.

Total: 17 closure comments anchor the 37 skip sites (some sites share a
single block-level comment). All skips remain in place; the change is
purely documentation. The audit recommendation was "audit each skip and
decide" — for these 37, the decision is uniformly **document-skip**:
the gating is correct, the t.Skip messages name the missing precondition,
and the closure comments now pin the rationale for future readers.

See coverage-gap-audit-2026-04-24-v5/unified-audit.md
cat-s3-58ce7e9840be for closure rationale.

cmd/agent/verify_test.go

@@ -391,7 +391,13 @@ func TestVerifyDeployment_FingerprintComparison(t *testing.T) {
 	}))
 	defer server.Close()
 
-	// Get the server's TLS certificate from TLS config
+	// Q-1 closure (cat-s3-58ce7e9840be): defensive skip — httptest.NewTLSServer
+	// always provisions a self-signed certificate at construction time, so this
+	// branch is currently unreachable in practice. Kept as a guard against
+	// future test-server constructions that swap in a custom *tls.Config with
+	// no Certificates slice (the path below dereferences server.TLS.Certificates[0]
+	// and would panic). The skip preserves the assertion logic for the normal
+	// fixture path; if it ever fires, it's a fixture bug, not a product bug.
 	if len(server.TLS.Certificates) == 0 {
 		t.Skip("no TLS certificates configured on test server")
 	}