feat: comprehensive NixOS support improvements (#1024)

* feat: comprehensive NixOS support improvements

This commit adds full NixOS support and automates Nix package maintenance:

## Static Linux Binaries for NixOS

Changes .goreleaser.yml to create static Linux binaries:
- Set CGO_ENABLED=0 for Linux amd64 and arm64 builds
- Remove cross-compiler dependencies (aarch64-linux-gnu-gcc)
- Simplifies build process while fixing NixOS compatibility

Static binaries work on all Linux distributions including NixOS, Alpine,
and musl-based distros without dynamic linker dependencies.

## Automated default.nix Version Management

Adds default.nix to the version bump workflow:
- Updates default.nix version field in bump-version.sh (new step 9)
- Adds default.nix to version verification checks
- Prevents version drift (was 5 releases behind: 0.42.0 vs 0.47.0)
- Updates README.md to remove glibc 2.32+ requirement

## Automated vendorHash Management

Creates scripts/update-nix-vendorhash.sh to automate vendorHash updates:
- Automatically detects correct hash by triggering Nix build error
- Extracts hash from error message and updates default.nix
- Verifies update with clean build
- Eliminates error-prone manual copy-paste workflow
- Works with local Nix OR Docker (uses nixos/nix image automatically)

Integrates vendorHash check into bump-version.sh:
- Detects when go.mod or go.sum have changed
- Prompts to run vendorHash update script interactively
- Catches synchronization issues at release time

## Documentation

Updates AGENTS.md with Nix package maintenance guide:
- Documents when and how to update vendorHash
- Recommends automated script as primary method
- Provides manual and alternative methods as fallback
- Notes Docker fallback for maintainers without Nix

## Impact

- NixOS users can now install via standard methods
- Nix package version stays synchronized automatically
- vendorHash updates work without Nix installed (via Docker)
- vendorHash updates are caught during release workflow
- All Linux users benefit from more portable binaries

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

* fix: address PR review feedback for NixOS support

Fixes three issues identified in PR review:

1. Replace undefined log_* functions in bump-version.sh with existing
   echo pattern (log_warning, log_info, log_success, log_error were
   called but not defined)

2. Update default.nix version from 0.42.0 to 0.47.0 to fix version
   drift with cmd/bd/version.go

3. Remove Nix Package Maintenance section from AGENTS.md per beads
   architecture (use bd prime for dynamic context, keep AGENTS.md
   minimal)

* fix: update versions to 0.47.1 after merge with main

- Update claude-plugin plugin.json to 0.47.1
- Update default.nix to 0.47.1
- Fixes version check failures after merging latest main branch

---------

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

scripts/bump-version.sh

@@ -305,6 +305,60 @@ main() {
         fi
     fi
 
+    # Check if go.mod or go.sum changed since last commit
+    if git diff HEAD go.mod go.sum 2>/dev/null | grep -q .; then
+        echo ""
+        echo -e "${YELLOW}Warning: go.mod or go.sum has uncommitted changes${NC}"
+        echo "You may need to update vendorHash in default.nix"
+        echo ""
+        read -p "Run ./scripts/update-nix-vendorhash.sh now? [y/N] " -n 1 -r
+        echo ""
+        if [[ $REPLY =~ ^[Yy]$ ]]; then
+            if [ -f "./scripts/update-nix-vendorhash.sh" ]; then
+                echo "Running vendorHash update script..."
+                if ./scripts/update-nix-vendorhash.sh; then
+                    echo -e "${GREEN}✓ vendorHash updated successfully${NC}"
+                else
+                    echo -e "${YELLOW}⚠ vendorHash update failed or was skipped${NC}"
+                fi
+                echo ""
+            else
+                echo -e "${RED}Error: scripts/update-nix-vendorhash.sh not found${NC}"
+                exit 1
+            fi
+        else
+            echo "Skipping vendorHash update"
+            echo "Run ./scripts/update-nix-vendorhash.sh manually if needed"
+            echo ""
+        fi
+    elif git diff HEAD~1..HEAD go.mod go.sum 2>/dev/null | grep -q .; then
+        # Check if go.mod/go.sum changed in the last commit
+        echo ""
+        echo -e "${YELLOW}Warning: go.mod or go.sum changed in the last commit${NC}"
+        echo "You may need to update vendorHash in default.nix"
+        echo ""
+        read -p "Run ./scripts/update-nix-vendorhash.sh now? [y/N] " -n 1 -r
+        echo ""
+        if [[ $REPLY =~ ^[Yy]$ ]]; then
+            if [ -f "./scripts/update-nix-vendorhash.sh" ]; then
+                echo "Running vendorHash update script..."
+                if ./scripts/update-nix-vendorhash.sh; then
+                    echo -e "${GREEN}✓ vendorHash updated successfully${NC}"
+                else
+                    echo -e "${YELLOW}⚠ vendorHash update failed or was skipped${NC}"
+                fi
+                echo ""
+            else
+                echo -e "${RED}Error: scripts/update-nix-vendorhash.sh not found${NC}"
+                exit 1
+            fi
+        else
+            echo "Skipping vendorHash update"
+            echo "Run ./scripts/update-nix-vendorhash.sh manually if needed"
+            echo ""
+        fi
+    fi
+
     echo "Updating version files..."
 
     # 1. Update cmd/bd/version.go
@@ -357,7 +411,13 @@ main() {
         "\"version\": \"$CURRENT_VERSION\"" \
         "\"version\": \"$NEW_VERSION\""
 
-    # 9. Update hook templates
+    # 9. Update default.nix (Nix package definition)
+    echo "  • default.nix"
+    update_file "default.nix" \
+        "version = \"$CURRENT_VERSION\";" \
+        "version = \"$NEW_VERSION\";"
+
+    # 10. Update hook templates
     echo "  • cmd/bd/templates/hooks/*"
     HOOK_FILES=("pre-commit" "post-merge" "pre-push" "post-checkout")
     for hook in "${HOOK_FILES[@]}"; do
@@ -366,7 +426,7 @@ main() {
             "# bd-hooks-version: $NEW_VERSION"
     done
 
-    # 10. Update CHANGELOG.md
+    # 11. Update CHANGELOG.md
     echo "  • CHANGELOG.md"
     update_changelog "$NEW_VERSION"
 
@@ -389,6 +449,7 @@ main() {
         "$(grep '__version__ = ' integrations/beads-mcp/src/beads_mcp/__init__.py | sed 's/.*"\(.*\)".*/\1/')"
         "$(jq -r '.version' npm-package/package.json)"
         "$(grep '# bd-hooks-version: ' cmd/bd/templates/hooks/pre-commit | sed 's/.*: \(.*\)/\1/')"
+        "$(grep 'version = ' default.nix | sed 's/.*"\(.*\)".*/\1/')"
     )
 
     ALL_MATCH=true