Initial implementation of vault-os

Complete implementation across all 13 phases:

- vault-core: types, YAML frontmatter parsing, entity classification,
  filesystem ops, config, prompt composition, validation, search
- vault-watch: filesystem watcher with daemon write filtering, event
  classification
- vault-scheduler: cron engine, process executor, task runner with
  retry logic and concurrency limiting
- vault-api: Axum REST API (15 route modules), WebSocket with broadcast,
  AI assistant proxy, validation, templates
- Dashboard: React + TypeScript + Tailwind v4 with kanban, CodeMirror
  editor, dynamic view system, AI chat sidebar
- Nix flake with dev shell and NixOS module
- Graceful shutdown, inotify overflow recovery, tracing instrumentation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Cargo.toml

@@ -0,0 +1,54 @@
+[workspace]
+members = ["crates/*"]
+resolver = "2"
+
+[workspace.package]
+version = "0.1.0"
+edition = "2021"
+license = "MIT OR Apache-2.0"
+authors = ["Harald Hoyer <harald@hoyer.xyz>"]
+
+[workspace.dependencies]
+serde = { version = "1", features = ["derive"] }
+serde_yaml = "0.9"
+serde_json = "1"
+chrono = { version = "0.4", features = ["serde"] }
+tracing = "0.1"
+tracing-subscriber = { version = "0.3", features = ["env-filter"] }
+thiserror = "2"
+anyhow = "1"
+uuid = { version = "1", features = ["v4", "serde"] }
+tokio = { version = "1", features = ["full"] }
+axum = { version = "0.8", features = ["ws"] }
+tower = "0.5"
+tower-http = { version = "0.6", features = ["cors", "trace", "fs"] }
+notify = "8"
+cron = "0.15"
+async-trait = "0.1"
+reqwest = { version = "0.12", features = ["json"] }
+clap = { version = "4", features = ["derive", "env"] }
+rust-embed = "8"
+pulldown-cmark = "0.12"
+
+vault-core = { path = "crates/vault-core" }
+vault-watch = { path = "crates/vault-watch" }
+vault-scheduler = { path = "crates/vault-scheduler" }
+vault-api = { path = "crates/vault-api" }
+
+[package]
+name = "vault-os"
+version.workspace = true
+edition.workspace = true
+
+[dependencies]
+vault-core.workspace = true
+vault-watch.workspace = true
+vault-scheduler.workspace = true
+vault-api.workspace = true
+tokio.workspace = true
+tracing.workspace = true
+tracing-subscriber.workspace = true
+clap.workspace = true
+anyhow.workspace = true
+axum.workspace = true
+chrono.workspace = true