fix(cve): CVE-2026-32280, CVE-2026-32281 - update Go from 1.25.8 to 1.25.9

- Update Go from 1.25.8 to 1.25.9 to address Go stdlib vulnerabilities
- CVE-2026-32280 (CVSS 7.5 HIGH): crypto/x509 DoS via certificate chain building
  All Go versions < 1.25.9 affected; fixed in 1.25.9
- CVE-2026-32281 (CVSS 7.5 HIGH): crypto/x509 DoS via inefficient certificate
  chain validation; fixed in Go 1.25.9

Changes:
- go.mod: go 1.25.8 → go 1.25.9
- go mod tidy, go mod verify, go mod vendor completed

Resolves: SRVKP-12045, SRVKP-12003

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Divyanshu Agrawal

go.mod

@@ -1,6 +1,6 @@
 module github.com/tektoncd/cli
 
-go 1.25.8
+go 1.25.9
 
 require (
 	github.com/AlecAivazis/survey/v2 v2.3.7