refactor: lowercase slug in gstack-slug and getRemoteSlug()

Fixes mixed-case slugs like Garry-s-List-garryslist by adding
tr '[:upper:]' '[:lower:]' to bash and .toLowerCase() to TypeScript.

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

bin/gstack-slug

@@ -3,7 +3,7 @@
 # Usage: eval $(gstack-slug)  → sets SLUG and BRANCH variables
 # Or:    gstack-slug           → prints SLUG=... and BRANCH=... lines
 set -euo pipefail
-SLUG=$(git remote get-url origin 2>/dev/null | sed 's|.*[:/]\([^/]*/[^/]*\)\.git$|\1|;s|.*[:/]\([^/]*/[^/]*\)$|\1|' | tr '/' '-')
+SLUG=$(git remote get-url origin 2>/dev/null | sed 's|.*[:/]\([^/]*/[^/]*\)\.git$|\1|;s|.*[:/]\([^/]*/[^/]*\)$|\1|' | tr '/' '-' | tr '[:upper:]' '[:lower:]')
 BRANCH=$(git rev-parse --abbrev-ref HEAD 2>/dev/null | tr '/' '-')
 echo "SLUG=$SLUG"
 echo "BRANCH=$BRANCH"

lib/util.ts

@@ -88,7 +88,7 @@ export function getRemoteSlug(): string {
     // SSH:   git@github.com:owner/repo.git → owner-repo
     // HTTPS: https://github.com/owner/repo.git → owner-repo
     const match = url.match(/[:/]([^/]+)\/([^/]+?)(?:\.git)?$/);
-    if (match) return `${match[1]}-${match[2]}`;
+    if (match) return `${match[1]}-${match[2]}`.toLowerCase();
     throw new Error('unparseable');
   } catch {
     const root = getGitRoot();