fix: move the Go toolchain to go1.26.9

.abcd/work/issues/resolved/iss-2610090821550872-go-toolchain-1-26-7-fails-govulncheck.md

@@ -0,0 +1,19 @@
+---
+schema_version: 1
+id: "iss-2610090821550872"
+slug: "go-toolchain-1-26-7-fails-govulncheck"
+severity: "major"
+category: "security"
+source: "agent-finding"
+found_during: "merge queue run 37897679940 (govulncheck job), 2026-10-09"
+origin: researcher-authored
+production_mode: hand-written
+found_at: "go.mod"
+remedy: "Bump go.mod's go directive to 1.26.9 (scripts/pinned-toolchain.sh and CI's setup-go follow it), run make preflight on the new toolchain, and confirm govulncheck passes; needs the user's dependency sign-off before it lands."
+resolution: "go.mod moved to go 1.26.9; govulncheck v1.7.0 reports no reachable vulnerability on that toolchain"
+impact: fix
+---
+
+main pins go 1.26.7 in go.mod, and govulncheck fails the merge queue (merge_group run 37897679940) on twelve stdlib advisories fixed in go1.26.9, among them GO-2026-6599 and GO-2026-6600 (html/template, reached through the dashboard page handler) and net/http traces.
+
+Verified 2026-10-09 with `GOTOOLCHAIN=go1.26.7 go run golang.org/x/vuln/cmd/govulncheck@latest ./...` at main 7549ca2d5: GO-2026-6617, -6613, -6612, -6611, -6610, -6605 and -6603 (net/http), GO-2026-6608 (net/textproto), GO-2026-6607 (crypto/tls), GO-2026-6604 (os), GO-2026-6600 and GO-2026-6599 (html/template, trace internal/surface/dashboard/server.go:274 `dashboard.servePage` calls `template.Template.Execute`), each fixed in go1.26.9.

go.mod

@@ -1,6 +1,6 @@
 module github.com/intentdriven/abcd
 
-go 1.26.7
+go 1.26.9
 
 require (
 	github.com/minio/selfupdate v0.6.0