[Repo Assist] refactor: add strutil.TruncateRunes and remove lookupEnrichmentToken alias (#3574)

🤖 *This PR was created by Repo Assist, an automated AI assistant.*

Three code quality improvements identified in #3564 (Semantic Function
Clustering Analysis).

## Changes

### 1. Add `strutil.TruncateRunes` (`internal/strutil/truncate.go`)

The codebase had a private `truncateForLog` in
`internal/proxy/graphql.go` that did rune-aware (Unicode-safe)
truncation — essential for non-ASCII content like CJK characters and
emoji. This logic is now exposed as `strutil.TruncateRunes(s string,
maxRunes int) string`, complementing the existing byte-based
`strutil.Truncate`.

9 table-driven tests added covering ASCII, multibyte (CJK), emoji, and
edge cases (zero/negative limit, empty string).

### 2. Delegate `truncateForLog` to `strutil.TruncateRunes`
(`internal/proxy/graphql.go`)

`truncateForLog` now calls `strutil.TruncateRunes`, removing the
duplicate implementation and centralising all truncation utilities in
the `strutil` package.

### 3. Inline `lookupEnrichmentToken` alias
(`internal/server/unified.go`)

`lookupEnrichmentToken()` was a zero-value wrapper — it called
`envutil.LookupGitHubToken()` and returned the result unchanged.
Inlining the single call site removes one unnecessary indirection layer
and makes the env-var lookup immediately visible at the call site.
(`lookupGitHubAPIBaseURL` is kept as-is since it adds a meaningful
default value.)

## Test Status

⚠️ **Infrastructure note**: The Go 1.25.0 toolchain required by `go.mod`
is not available in the CI agent environment (blocked by network
firewall; only Go 1.24.13 is installed locally). All three changes are
syntactically straightforward — no new language features, no interface
changes. Tests will run in the GitHub Actions CI environment where Go
1.25.0 is available.

## Trade-offs

- `TruncateRunes` uses `[]rune(s)` conversion, which allocates. This is
intentional: rune-safe truncation by definition requires decoding all
codepoints up to the limit. The function is only used in debug-log paths
where this is acceptable.
- `truncateForLog` is kept as a package-private shim (rather than
inlined) to preserve the semantic name at the two call sites inside
`graphql.go`.

Closes: no issue (addresses items from analysis report #3564)
Ref: #3564




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Author: lpcox

internal/proxy/graphql.go

@@ -6,6 +6,7 @@ import (
 	"strings"
 
 	"github.com/github/gh-aw-mcpg/internal/logger"
+	"github.com/github/gh-aw-mcpg/internal/strutil"
 )
 
 var logGraphQL = logger.New("proxy:graphql")
@@ -191,14 +192,7 @@ var searchQueryArgPattern = regexp.MustCompile(`(?i)\bsearch\s*\(\s*query\s*:\s*
 
 // truncateForLog truncates s to at most maxRunes runes, for safe debug logging.
 func truncateForLog(s string, maxRunes int) string {
-	if maxRunes <= 0 {
-		return ""
-	}
-	r := []rune(s)
-	if len(r) <= maxRunes {
-		return s
-	}
-	return string(r[:maxRunes])
+	return strutil.TruncateRunes(s, maxRunes)
 }
 
 // extractSearchQuery returns the search query argument from a GraphQL search

internal/server/unified.go

@@ -279,7 +279,7 @@ func (g *guardBackendCaller) callCollaboratorPermission(ctx context.Context, arg
 		return nil, fmt.Errorf("get_collaborator_permission: missing owner/repo/username")
 	}
 
-	token := lookupEnrichmentToken()
+	token := envutil.LookupGitHubToken()
 	if token == "" {
 		logUnified.Printf("get_collaborator_permission: no GitHub token available for %s/%s user %s, skipping", owner, repo, username)
 		return nil, fmt.Errorf("get_collaborator_permission: no GitHub token available")
@@ -338,12 +338,6 @@ func (g *guardBackendCaller) callCollaboratorPermission(ctx context.Context, arg
 	return mcpResp, nil
 }
 
-// lookupEnrichmentToken searches environment variables for a GitHub token
-// suitable for enrichment API calls.
-func lookupEnrichmentToken() string {
-	return envutil.LookupGitHubToken()
-}
-
 // lookupGitHubAPIBaseURL returns the GitHub API base URL from environment
 // or defaults to https://api.github.com.
 func lookupGitHubAPIBaseURL() string {

internal/strutil/truncate.go

@@ -29,3 +29,18 @@ func TruncateWithSuffix(s string, maxLen int, suffix string) string {
 	}
 	return s[:maxLen] + suffix
 }
+
+// TruncateRunes truncates s to at most maxRunes Unicode code points (runes).
+// Unlike Truncate, which counts bytes, TruncateRunes is safe for non-ASCII
+// content (e.g. emoji, CJK characters). If maxRunes is 0 or negative, returns
+// an empty string.
+func TruncateRunes(s string, maxRunes int) string {
+	if maxRunes <= 0 {
+		return ""
+	}
+	r := []rune(s)
+	if len(r) <= maxRunes {
+		return s
+	}
+	return string(r[:maxRunes])
+}

internal/strutil/truncate_test.go

@@ -146,3 +146,74 @@ func TestTruncateWithSuffix(t *testing.T) {
 		})
 	}
 }
+
+func TestTruncateRunes(t *testing.T) {
+	tests := []struct {
+		name      string
+		input     string
+		maxRunes  int
+		expected  string
+	}{
+		{
+			name:     "ASCII string within limit",
+			input:    "hello",
+			maxRunes: 10,
+			expected: "hello",
+		},
+		{
+			name:     "ASCII string exactly at limit",
+			input:    "hello",
+			maxRunes: 5,
+			expected: "hello",
+		},
+		{
+			name:     "ASCII string exceeds limit",
+			input:    "hello world",
+			maxRunes: 5,
+			expected: "hello",
+		},
+		{
+			name:     "multibyte runes within limit",
+			input:    "日本語",
+			maxRunes: 5,
+			expected: "日本語",
+		},
+		{
+			name:     "multibyte runes truncated",
+			input:    "日本語テスト",
+			maxRunes: 3,
+			expected: "日本語",
+		},
+		{
+			name:     "emoji truncated",
+			input:    "😀😁😂😃😄",
+			maxRunes: 3,
+			expected: "😀😁😂",
+		},
+		{
+			name:     "zero maxRunes returns empty",
+			input:    "hello",
+			maxRunes: 0,
+			expected: "",
+		},
+		{
+			name:     "negative maxRunes returns empty",
+			input:    "hello",
+			maxRunes: -1,
+			expected: "",
+		},
+		{
+			name:     "empty string",
+			input:    "",
+			maxRunes: 10,
+			expected: "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := TruncateRunes(tt.input, tt.maxRunes)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}