Security patch: bump Go 1.26.3 and gomarkdown (#1073)

## What changed?

Security-only dependency bumps for CLI v1.7.1, shipping in the OSS
server v1.31.1 admin-tools image.

- Go toolchain 1.26.2 -> 1.26.3 — clears stdlib HIGH CVEs visible in
admin-tools image scans (CVE-2026-39820, -42499, -39836, -33814, -33811,
-42501).
- github.com/gomarkdown/markdown v0.0.0-20250311... ->
v0.0.0-20260411013819-759bbc3e3207 — clears GHSA-77fj-vx54-gvh7 /
CVE-2026-40890. Indirect dep pulled in via the embedded UI server.

Author: fretz12

go.mod

@@ -1,6 +1,6 @@
 module github.com/temporalio/cli
 
-go 1.26.2
+go 1.26.3
 
 require (
 	github.com/BurntSushi/toml v1.4.0
@@ -103,7 +103,7 @@ require (
 	github.com/golang-jwt/jwt/v4 v4.5.2 // indirect
 	github.com/golang/mock v1.7.0-rc.1 // indirect
 	github.com/golang/snappy v1.0.0 // indirect
-	github.com/gomarkdown/markdown v0.0.0-20250311123330-531bef5e742b // indirect
+	github.com/gomarkdown/markdown v0.0.0-20260411013819-759bbc3e3207 // indirect
 	github.com/google/gnostic-models v0.7.0 // indirect
 	github.com/google/s2a-go v0.1.9 // indirect
 	github.com/googleapis/enterprise-certificate-proxy v0.3.7 // indirect

go.sum

@@ -197,8 +197,8 @@ github.com/golang/protobuf v1.5.4/go.mod h1:lnTiLA8Wa4RWRcIUkrtSVa5nRhsEGBg48fD6
 github.com/golang/snappy v0.0.3/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
 github.com/golang/snappy v1.0.0 h1:Oy607GVXHs7RtbggtPBnr2RmDArIsAefDwvrdWvRhGs=
 github.com/golang/snappy v1.0.0/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
-github.com/gomarkdown/markdown v0.0.0-20250311123330-531bef5e742b h1:EY/KpStFl60qA17CptGXhwfZ+k1sFNJIUNR8DdbcuUk=
-github.com/gomarkdown/markdown v0.0.0-20250311123330-531bef5e742b/go.mod h1:JDGcbDT52eL4fju3sZ4TeHGsQwhG9nbDV21aMyhwPoA=
+github.com/gomarkdown/markdown v0.0.0-20260411013819-759bbc3e3207 h1:p7t34F7K4OCRQblcDhNJnP46Uaarz3z2cLcvOZYxWn8=
+github.com/gomarkdown/markdown v0.0.0-20260411013819-759bbc3e3207/go.mod h1:JDGcbDT52eL4fju3sZ4TeHGsQwhG9nbDV21aMyhwPoA=
 github.com/google/gnostic-models v0.7.0 h1:qwTtogB15McXDaNqTZdzPJRHvaVJlAl+HVQnLmJEJxo=
 github.com/google/gnostic-models v0.7.0/go.mod h1:whL5G0m6dmc5cPxKc5bdKdEN3UjI7OUGxBlw57miDrQ=
 github.com/google/go-cmp v0.5.4/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=