Add terminal package with secure ReadPassword helper

Provides echo-suppressed password prompting via golang.org/x/term for
CLI login commands. Added as a platform standard in engineering-standards.md.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -37,6 +37,7 @@ go test ./auth/ -run TestCacheExpiry
 | `web` | Session cookies, auth middleware, template rendering for htmx UIs |
 | `health` | REST and gRPC health check handlers |
 | `archive` | tar.zst snapshots with SQLite-aware backup (VACUUM INTO) |
+| `terminal` | Secure terminal input (echo-suppressed password prompts) |
 
 ## Import Pattern
 
@@ -63,6 +64,7 @@ db --> (modernc.org/sqlite)
 grpcserver --> auth, config
 health --> db
 httpserver --> config
+terminal --> (golang.org/x/term)
 web --> auth, csrf
 ```
 

go.mod

@@ -18,6 +18,7 @@ require (
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
 	golang.org/x/net v0.48.0 // indirect
 	golang.org/x/sys v0.42.0 // indirect
+	golang.org/x/term v0.41.0 // indirect
 	golang.org/x/text v0.32.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20251202230838-ff82c1b0f217 // indirect
 	google.golang.org/protobuf v1.36.10 // indirect

go.sum

@@ -49,6 +49,8 @@ golang.org/x/sync v0.19.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.42.0 h1:omrd2nAlyT5ESRdCLYdm3+fMfNFE/+Rf4bDIQImRJeo=
 golang.org/x/sys v0.42.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
+golang.org/x/term v0.41.0 h1:QCgPso/Q3RTJx2Th4bDLqML4W6iJiaXFq2/ftQF13YU=
+golang.org/x/term v0.41.0/go.mod h1:3pfBgksrReYfZ5lvYM0kSO0LIkAl4Yl2bXOkKP7Ec2A=
 golang.org/x/text v0.32.0 h1:ZD01bjUt1FQ9WJ0ClOL5vxgxOI/sVCNgX1YtKwcY0mU=
 golang.org/x/text v0.32.0/go.mod h1:o/rUWzghvpD5TXrTIBuJU77MTaN0ljMWE47kxGJQ7jY=
 golang.org/x/tools v0.42.0 h1:uNgphsn75Tdz5Ji2q36v/nsFSfR/9BRFvqhGBaJGd5k=

terminal/terminal.go

@@ -0,0 +1,22 @@
+// Package terminal provides secure terminal input helpers for CLI tools.
+package terminal
+
+import (
+	"fmt"
+	"os"
+
+	"golang.org/x/term"
+)
+
+// ReadPassword prints the given prompt to stderr and reads a password
+// from the terminal with echo disabled. It prints a newline after the
+// input is complete so the cursor advances normally.
+func ReadPassword(prompt string) (string, error) {
+	fmt.Fprint(os.Stderr, prompt)
+	b, err := term.ReadPassword(int(os.Stdin.Fd())) //nolint:gosec // fd fits in int
+	fmt.Fprintln(os.Stderr)
+	if err != nil {
+		return "", err
+	}
+	return string(b), nil
+}

terminal/terminal_test.go

@@ -0,0 +1,14 @@
+package terminal
+
+import (
+	"testing"
+)
+
+func TestReadPasswordNotATTY(t *testing.T) {
+	// When stdin is not a terminal (e.g. in CI), ReadPassword should
+	// return an error rather than hanging or panicking.
+	_, err := ReadPassword("Password: ")
+	if err == nil {
+		t.Fatal("expected error when stdin is not a terminal")
+	}
+}