feat: add lab-monitoring MCP server for Prometheus and Alertmanager

New MCP server that queries live Prometheus and Alertmanager HTTP APIs
with 8 tools: list_alerts, get_alert, search_metrics, get_metric_metadata,
query (PromQL), list_targets, list_silences, and create_silence.

Extends the MCP core with ModeCustom and NewGenericServer for servers
that don't require a database. Includes CLI with direct commands
(alerts, query, targets, metrics), NixOS module, and comprehensive
httptest-based tests.

Bumps existing binaries to 0.2.1 due to shared internal/mcp change.

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

CLAUDE.md

@@ -20,7 +20,12 @@ Search and query NixOS configuration options. Uses nixpkgs as source.
 ### Home Manager Options (`hm-options`)
 Search and query Home Manager configuration options. Uses home-manager repository as source.
 
-All servers share the same architecture:
+### Lab Monitoring (`lab-monitoring`)
+Query Prometheus metrics and Alertmanager alerts. Unlike other servers, this queries live HTTP APIs — no database or indexing needed.
+- 8 tools: list/get alerts, search metrics, get metadata, PromQL query, list targets, list/create silences
+- Configurable Prometheus and Alertmanager URLs via flags or environment variables
+
+The nixpkgs/options/hm servers share a database-backed architecture:
 - Full-text search across option/package names and descriptions
 - Query specific options/packages with full metadata
 - Index multiple revisions (by git hash or channel name)
@@ -38,8 +43,9 @@ All servers share the same architecture:
 ## Project Status
 
 **Complete and maintained** - All core features implemented:
-- Full MCP servers with 6 tools each
-- PostgreSQL and SQLite backends with FTS
+- Full MCP servers (6 tools each for nixpkgs/options, 8 tools for monitoring)
+- PostgreSQL and SQLite backends with FTS (for nixpkgs/options servers)
+- Live API queries for Prometheus/Alertmanager (monitoring server)
 - NixOS modules for deployment
 - CLI for manual operations
 - Comprehensive test suite
@@ -53,8 +59,10 @@ labmcp/
 │   │   └── main.go             # Combined options+packages CLI (primary)
 │   ├── nixos-options/
 │   │   └── main.go             # NixOS options CLI (legacy)
-│   └── hm-options/
-│       └── main.go             # Home Manager options CLI
+│   ├── hm-options/
+│   │   └── main.go             # Home Manager options CLI
+│   └── lab-monitoring/
+│       └── main.go             # Prometheus/Alertmanager CLI
 ├── internal/
 │   ├── database/
 │   │   ├── interface.go        # Store interface (options + packages)
@@ -82,15 +90,23 @@ labmcp/
 │   │   ├── indexer.go          # Home Manager indexing
 │   │   ├── types.go            # Channel aliases, extensions
 │   │   └── *_test.go           # Indexer tests
-│   └── packages/
-│       ├── indexer.go          # Nix packages indexing
-│       ├── parser.go           # nix-env JSON parsing
-│       ├── types.go            # Package types, channel aliases
-│       └── *_test.go           # Parser tests
+│   ├── packages/
+│   │   ├── indexer.go          # Nix packages indexing
+│   │   ├── parser.go           # nix-env JSON parsing
+│   │   ├── types.go            # Package types, channel aliases
+│   │   └── *_test.go           # Parser tests
+│   └── monitoring/
+│       ├── types.go            # Prometheus/Alertmanager API types
+│       ├── prometheus.go       # Prometheus HTTP client
+│       ├── alertmanager.go     # Alertmanager HTTP client
+│       ├── handlers.go         # MCP tool definitions + handlers
+│       ├── format.go           # Markdown formatting utilities
+│       └── *_test.go           # Tests (httptest-based)
 ├── nix/
-│   ├── module.nix              # NixOS module for nixos-options
-│   ├── hm-options-module.nix   # NixOS module for hm-options
-│   └── package.nix             # Parameterized Nix package
+│   ├── module.nix                  # NixOS module for nixos-options
+│   ├── hm-options-module.nix       # NixOS module for hm-options
+│   ├── lab-monitoring-module.nix   # NixOS module for lab-monitoring
+│   └── package.nix                 # Parameterized Nix package
 ├── testdata/
 │   └── options-sample.json     # Test fixture
 ├── flake.nix
@@ -124,6 +140,19 @@ labmcp/
 | `list_revisions` | List all indexed revisions |
 | `delete_revision` | Delete an indexed revision |
 
+### Monitoring Server (lab-monitoring)
+
+| Tool | Description |
+|------|-------------|
+| `list_alerts` | List alerts with optional filters (state, severity, receiver) |
+| `get_alert` | Get full details for a specific alert by fingerprint |
+| `search_metrics` | Search metric names with substring filter, enriched with metadata |
+| `get_metric_metadata` | Get type, help text, and unit for a specific metric |
+| `query` | Execute instant PromQL query |
+| `list_targets` | List scrape targets with health status |
+| `list_silences` | List active/pending silences |
+| `create_silence` | Create a silence (confirms with user first) |
+
 ## Key Implementation Details
 
 ### Database
@@ -212,6 +241,17 @@ hm-options delete <revision>           # Delete indexed revision
 hm-options --version                   # Show version
 ```
 
+### lab-monitoring
+```bash
+lab-monitoring serve                          # Run MCP server on STDIO
+lab-monitoring serve --transport http         # Run MCP server on HTTP
+lab-monitoring alerts                         # List alerts
+lab-monitoring alerts --state active          # Filter by state
+lab-monitoring query 'up'                     # Instant PromQL query
+lab-monitoring targets                        # List scrape targets
+lab-monitoring metrics node                   # Search metric names
+```
+
 ### Channel Aliases
 
 **nixpkgs-search/nixos-options**: `nixos-unstable`, `nixos-stable`, `nixos-24.11`, `nixos-24.05`, etc.
@@ -220,6 +260,9 @@ hm-options --version                   # Show version
 
 ## Notes for Claude
 
+### Planning
+When creating implementation plans, the first step should usually be to **checkout an appropriately named feature branch** (e.g., `git checkout -b feature/lab-monitoring`). This keeps work isolated and makes PRs cleaner.
+
 ### Development Workflow
 - **Always run `go fmt ./...` before committing Go code**
 - **Run Go commands using `nix develop -c`** (e.g., `nix develop -c go test ./...`)
@@ -257,7 +300,8 @@ Version is defined in multiple places that must stay in sync:
 - `cmd/nixpkgs-search/main.go`
 - `cmd/nixos-options/main.go`
 - `cmd/hm-options/main.go`
-- `internal/mcp/server.go` (in `DefaultNixOSConfig`, `DefaultHomeManagerConfig`, `DefaultNixpkgsPackagesConfig`)
+- `cmd/lab-monitoring/main.go`
+- `internal/mcp/server.go` (in `DefaultNixOSConfig`, `DefaultHomeManagerConfig`, `DefaultNixpkgsPackagesConfig`, `DefaultMonitoringConfig`)
 - `nix/package.nix`
 
 ### User Preferences
@@ -284,6 +328,7 @@ nix develop -c go test -bench=. -benchtime=1x -timeout=30m ./internal/homemanage
 nix build .#nixpkgs-search
 nix build .#nixos-options
 nix build .#hm-options
+nix build .#lab-monitoring
 
 # Run directly
 nix run .#nixpkgs-search -- options serve
@@ -291,6 +336,7 @@ nix run .#nixpkgs-search -- packages serve
 nix run .#nixpkgs-search -- index nixos-unstable
 nix run .#hm-options -- serve
 nix run .#hm-options -- index hm-unstable
+nix run .#lab-monitoring -- serve
 ```
 
 ### Indexing Performance