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>

.goreleaser.yml

@@ -13,7 +13,7 @@ builds:
     main: ./cmd/bd
     binary: bd
     env:
-      - CGO_ENABLED=1
+      - CGO_ENABLED=0
     goos:
       - linux
     goarch:
@@ -29,9 +29,7 @@ builds:
     main: ./cmd/bd
     binary: bd
     env:
-      - CGO_ENABLED=1
-      - CC=aarch64-linux-gnu-gcc
-      - CXX=aarch64-linux-gnu-g++
+      - CGO_ENABLED=0
     goos:
       - linux
     goarch: