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.

src/config.rs

@@ -0,0 +1,76 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Config {
+    pub server: ServerConfig,
+    pub forgejo: ForgejoConfig,
+    pub matrix: MatrixConfig,
+    pub orchestrator: OrchestratorConfig,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ServerConfig {
+    pub bind: String,
+    pub port: u16,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ForgejoConfig {
+    pub url: String,
+    pub token: String,
+    pub webhook_secret: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct MatrixConfig {
+    pub homeserver_url: String,
+    pub user_id: String,
+    pub access_token: String,
+    pub room_id: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct OrchestratorConfig {
+    pub db_path: String,
+    pub heartbeat_interval_secs: u64,
+    pub heartbeat_timeout_threshold: u32,
+    pub task_timeout_secs: u64,
+    pub default_max_retries: u32,
+}
+
+impl Default for Config {
+    fn default() -> Self {
+        Self {
+            server: ServerConfig {
+                bind: "0.0.0.0".into(),
+                port: 9090,
+            },
+            forgejo: ForgejoConfig {
+                url: "https://git.0x08.org".into(),
+                token: String::new(),
+                webhook_secret: String::new(),
+            },
+            matrix: MatrixConfig {
+                homeserver_url: "https://matrix.0x08.org".into(),
+                user_id: "@jeeves:0x08.org".into(),
+                access_token: String::new(),
+                room_id: String::new(),
+            },
+            orchestrator: OrchestratorConfig {
+                db_path: "data/agent-fleet.db".into(),
+                heartbeat_interval_secs: 60,
+                heartbeat_timeout_threshold: 3,
+                task_timeout_secs: 1800,
+                default_max_retries: 2,
+            },
+        }
+    }
+}
+
+impl Config {
+    pub fn load(path: &str) -> Result<Self, Box<dyn std::error::Error>> {
+        let content = std::fs::read_to_string(path)?;
+        let config: Config = toml::from_str(&content)?;
+        Ok(config)
+    }
+}