Remove dead IsStdoutTerminal() and simplify containsAny test helper (#1494)

Two quick-win cleanups from the `golang.org/x/term` module review.

## Changes

- **`internal/tty/tty.go`**: Remove `IsStdoutTerminal()` — exported but
never called anywhere in the project. `IsStderrTerminal()` (used by the
logger) is retained.

- **`internal/tty/container_test.go`**: Replace hand-rolled substring
search in the `containsAny` helper with `strings.Contains`:

```go
// Before: manual nested loop
func containsAny(s string, substrings []string) bool {
    for _, substr := range substrings {
        if len(s) >= len(substr) {
            for i := 0; i <= len(s)-len(substr); i++ {
                if s[i:i+len(substr)] == substr {
                    return true
                }
            }
        }
    }
    return false
}

// After: standard library
func containsAny(s string, substrings []string) bool {
    for _, substr := range substrings {
        if strings.Contains(s, substr) {
            return true
        }
    }
    return false
}
```

> [!WARNING]
>
> <details>
> <summary>Firewall rules blocked me from connecting to one or more
addresses (expand for details)</summary>
>
> #### I tried to connect to the following addresses, but was blocked by
firewall rules:
>
> - `example.com`
> - Triggering command: `/tmp/go-build609076577/b298/launcher.test
/tmp/go-build609076577/b298/launcher.test
-test.testlogfile=/tmp/go-build609076577/b298/testlog.txt
-test.paniconexit0 -test.timeout=10m0s -test.v=true 64/src/runtime/cgo
64/src/internal/fmtsort/sort.go x_amd64/compile user.name 7533934/b010/`
(dns block)
> - `invalid-host-that-does-not-exist-12345.com`
> - Triggering command: `/tmp/go-build609076577/b280/config.test
/tmp/go-build609076577/b280/config.test
-test.testlogfile=/tmp/go-build609076577/b280/testlog.txt
-test.paniconexit0 -test.timeout=10m0s -test.v=true 64/src/runtime/cgo
40tls/fipstls.go ache/go/1.25.7/x64/pkg/tool/linu-o
credential.helpe/opt/hostedtoolcache/go/1.25.7/x64/pkg/tool/linux_amd64/vet`
(dns block)
> - `nonexistent.local`
> - Triggering command: `/tmp/go-build609076577/b298/launcher.test
/tmp/go-build609076577/b298/launcher.test
-test.testlogfile=/tmp/go-build609076577/b298/testlog.txt
-test.paniconexit0 -test.timeout=10m0s -test.v=true 64/src/runtime/cgo
64/src/internal/fmtsort/sort.go x_amd64/compile user.name 7533934/b010/`
(dns block)
> - `slow.example.com`
> - Triggering command: `/tmp/go-build609076577/b298/launcher.test
/tmp/go-build609076577/b298/launcher.test
-test.testlogfile=/tmp/go-build609076577/b298/testlog.txt
-test.paniconexit0 -test.timeout=10m0s -test.v=true 64/src/runtime/cgo
64/src/internal/fmtsort/sort.go x_amd64/compile user.name 7533934/b010/`
(dns block)
> - `this-host-does-not-exist-12345.com`
> - Triggering command: `/tmp/go-build609076577/b307/mcp.test
/tmp/go-build609076577/b307/mcp.test
-test.testlogfile=/tmp/go-build609076577/b307/testlog.txt
-test.paniconexit0 -test.timeout=10m0s -test.v=true arm.go --local
x_amd64/compile user.name /gc` (dns block)
>
> If you need me to access, download, or install something from one of
these locations, you can either:
>
> - Configure [Actions setup
steps](https://gh.io/copilot/actions-setup-steps) to set up my
environment, which run before the firewall is enabled
> - Add the appropriate URLs or hosts to the custom allowlist in this
repository's [Copilot coding agent
settings](https://github.com/github/gh-aw-mcpg/settings/copilot/coding_agent)
(admins only)
>
> </details>

<!-- START COPILOT ORIGINAL PROMPT -->



<details>

<summary>Original prompt</summary>


----

*This section details on the original issue you should resolve*

<issue_title>[go-fan] Go Module Review: golang.org/x/term</issue_title>
<issue_description># 🐹 Go Fan Report: golang.org/x/term

## Module Overview
`golang.org/x/term` is the official Go extended library for
cross-platform terminal handling. It provides terminal detection, mode
switching (raw mode), terminal sizing, password reading, and a full
line-editing terminal emulator. It supports Linux, macOS, Windows, and
Plan9.

## Current Usage in gh-aw
The module is used exclusively through the thin `internal/tty` wrapper
package.

- **Files**: 1 file imports the module (`internal/tty/tty.go`)
- **Import count**: 1 direct import
- **Key APIs Used**:
- `term.IsTerminal(int(os.Stderr.Fd()))` — checks stderr is a TTY, used
at init in `internal/logger/logger.go` to enable ANSI color output
- `term.IsTerminal(int(os.Stdout.Fd()))` — defined as
`IsStdoutTerminal()` in the tty package but **never called anywhere** in
the project

## Research Findings
`golang.org/x/term` v0.38.0 is the current version in use. The most
recent activity (Feb 11, 2026) was a routine Go directive update to
1.25.0 — no new user-facing APIs were added. The module API has been
stable for years.

### Available APIs (not yet used)
| API | Description |
|-----|-------------|
| `GetSize(fd int)` | Returns terminal width and height |
| `ReadPassword(fd int)` | Reads a password without echo |
| `MakeRaw(fd int)` | Puts terminal in raw mode |
| `Restore(fd int, state)` | Restores terminal state |
| `NewTerminal(rw, prompt)` | Full line-editing terminal emulator |

### Best Practices
- Wrapping `golang.org/x/term` in an internal package (as this project
does in `internal/tty`) is the recommended approach — it prevents the
dependency from spreading throughout the codebase and makes it easy to
mock/test.
- The `int(os.Stderr.Fd())` cast pattern is idiomatic and correct.

## Improvement Opportunities

### 🏃 Quick Wins

1. **Remove dead code: `IsStdoutTerminal()`**
- `IsStdoutTerminal()` in `internal/tty/tty.go` (line 13) is **never
called** anywhere in the project.
   - Either add a caller or remove this exported function.
- Dead exported functions in internal packages create confusion about
intent.

2. **Simplify `containsAny` test helper in `container_test.go`**
- The `containsAny` helper (lines 313–325) reimplements substring search
with a manual nested loop:
     ```go
     for i := 0; i <= len(s)-len(substr); i++ {
         if s[i:i+len(substr)] == substr {
             return true
         }
     }
     ```
- This should use `strings.Contains` from the standard library, which is
simpler, more readable, and better optimized:
     ```go
     func containsAny(s string, substrings []string) bool {
         for _, substr := range substrings {
             if strings.Contains(s, substr) {
                 return true
             }
         }
         return false
     }
     ```

### ✨ Feature Opportunities

3. **Terminal width-aware log output**
- `term.GetSize(int(os.Stderr.Fd()))` could be used in the logger to
adapt log line width to the terminal width.
- Currently, the logger enables/disables color based on TTY detection
but never adapts output width. Long debug lines could be wrapped or
truncated at the terminal width for better readability.

4. **Password/secret prompting at startup**
- If the gateway ever needs to prompt users interactively for API keys
or credentials (e.g., when running without a config file),
`term.ReadPassword()` is already available via the existing dependency
at zero extra cost.

### 📐 Best Practice Alignment

- ✅ Wrapping in `internal/tty` is correct and idiomatic
- ✅ `int(os.Fd())` cast pattern is standard
- ⚠️ `IsStdoutTerminal()` exported but unused — either use it or remove
it
- ⚠️ Test helper `containsAny` should use `strings.Contains`

### 🔧 General Improvements

The `internal/tty` package currently mixes two concerns: terminal
detection (`tty.go`) and container detection (`container.go`). These
could eventually be split into separate focused packages (`internal/tty`
and `internal/container`), but this is low priority since the package is
small.

## Recommendations

1. **[High Priority]** Remove or add a caller for `IsStdoutTerminal()` —
dead exported code is confusing
2. **[Medium Priority]** Replace `containsAny` manual loop with
`strings.Contains` — simpler and more standard
3. **[Low Priority]** Consider `term.GetSize()` for terminal-width-aware
formatting in the logger

## Next Steps
- [ ] Decide whether `IsStdoutTerminal()` should be removed or used
somewhere (e.g., in a future stdout color detection path)
- [ ] Update `containsAny` test helper to use `strings.Contains`

---
*Generated by Go Fan 🐹*
*Module summary saved to: `/tmp/gh-aw/agent/term-module-summary.md`
(workspace write permission not available for specs/mods/)*
*Run:
[§22476915418](https://github.com/github/gh-aw-mcpg/actions/runs/22476915418)*

**Ref...

</details>


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- Fixes #1459

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Author: lpcox

internal/tty/container_test.go

@@ -2,6 +2,7 @@ package tty
 
 import (
 	"os"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -312,12 +313,8 @@ func TestIsRunningInContainer_ConcurrentAccess(t *testing.T) {
 // Helper function to check if a string contains any of the given substrings
 func containsAny(s string, substrings []string) bool {
 	for _, substr := range substrings {
-		if len(s) >= len(substr) {
-			for i := 0; i <= len(s)-len(substr); i++ {
-				if s[i:i+len(substr)] == substr {
-					return true
-				}
-			}
+		if strings.Contains(s, substr) {
+			return true
 		}
 	}
 	return false

internal/tty/tty.go

@@ -9,11 +9,6 @@ import (
 	"golang.org/x/term"
 )
 
-// IsStdoutTerminal returns true if stdout is connected to a terminal.
-func IsStdoutTerminal() bool {
-	return term.IsTerminal(int(os.Stdout.Fd()))
-}
-
 // IsStderrTerminal returns true if stderr is connected to a terminal.
 func IsStderrTerminal() bool {
 	return term.IsTerminal(int(os.Stderr.Fd()))