feat: implement orchestrator core (Rust)

Task 1.1: ✅ Cargo.toml with axum, rusqlite, matrix-sdk, serde, etc.
Task 1.2: ✅ Directory structure: src/core, src/adapters, src/integrations, src/api
Task 1.5: ✅ config.example.toml with full schema
Task 2.1: ✅ Data models: Agent, Task, Receipt, Artifact, TaskEvent
Task 2.2: ✅ Event Store: SQLite append-only with task/agent tables
Task 2.3: ✅ Task state machine: created→assigned→running→completed/failed
Task 2.4: ✅ Global task queue with priority ordering
Task 2.5: ✅ Background timeout checker
Task 2.6: ✅ Retry policy with configurable max_retries

Compiles clean (warnings only, no errors).
API handler stubs in place for Phase 2.

Cargo.toml

@@ -0,0 +1,45 @@
+[package]
+name = "agent-fleet"
+version = "0.1.0"
+edition = "2024"
+description = "Agent Fleet Platform - Multi-agent orchestration with Forgejo + Matrix"
+license = "MIT"
+
+[dependencies]
+# Web framework
+axum = { version = "0.8", features = ["macros"] }
+tokio = { version = "1", features = ["full"] }
+tower = "0.5"
+tower-http = { version = "0.6", features = ["cors", "trace"] }
+
+# Serialization
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+
+# Database
+rusqlite = { version = "0.32", features = ["bundled"] }
+
+# Configuration
+toml = "0.8"
+
+# HTTP client (for Forgejo API, Matrix API)
+reqwest = { version = "0.12", features = ["json"] }
+
+# Matrix SDK
+matrix-sdk = "0.10"
+
+# Logging
+tracing = "0.1"
+tracing-subscriber = { version = "0.3", features = ["env-filter", "json"] }
+
+# CLI
+clap = { version = "4", features = ["derive"] }
+
+# Utils
+uuid = { version = "1", features = ["v4", "serde"] }
+chrono = { version = "0.4", features = ["serde"] }
+thiserror = "2"
+async-trait = "0.1"
+
+[dev-dependencies]
+tempfile = "3"