feat(ptc): programmatic tool calling -- executor, SDK, and E2E tests

Add ToolExecutor for standalone tool dispatch used by both the
orchestrator HTTP RPC endpoint and the WASM tool_invoke host function.
Includes Python SDK for container scripts, WASM test fixture, and
comprehensive E2E test coverage across all PTC paths.

Implementation:
- ToolExecutor with timeout, nesting depth limit, safety sanitization
- Orchestrator POST /worker/{job_id}/tools/call endpoint with SSE events
- WASM tool_invoke host function with alias resolution
- Python SDK (stdlib-only) with call_tool + convenience wrappers

Tests (16 new):
- 6 orchestrator HTTP RPC tests (auth, echo, not-found, timeout, SSE, no-executor)
- 3 executor integration tests (sanitization, invalid params, sequential)
- 4 Python SDK tests (env vars, request format, HTTP error, wrappers)
- 3 WASM E2E tests (echo via alias, alias not granted, no capability)

Refs #407

Co-Authored-By: Claude Opus 4.6 <[email protected]>

tools-src/test-ptc/Cargo.toml

@@ -0,0 +1,20 @@
+[package]
+name = "test-ptc-tool"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[dependencies]
+wit-bindgen = "0.41.0"
+serde_json = "1.0"
+
+[lib]
+crate-type = ["cdylib"]
+
+[profile.release]
+opt-level = "s"
+lto = true
+strip = true
+codegen-units = 1
+
+[workspace]

tools-src/test-ptc/src/lib.rs

@@ -0,0 +1,52 @@
+wit_bindgen::generate!({
+    world: "sandboxed-tool",
+    path: "../../wit/tool.wit",
+});
+
+struct TestPtcTool;
+
+impl exports::near::agent::tool::Guest for TestPtcTool {
+    fn execute(req: exports::near::agent::tool::Request) -> exports::near::agent::tool::Response {
+        match execute_inner(&req.params) {
+            Ok(result) => exports::near::agent::tool::Response {
+                output: Some(result),
+                error: None,
+            },
+            Err(e) => exports::near::agent::tool::Response {
+                output: None,
+                error: Some(e),
+            },
+        }
+    }
+
+    fn schema() -> String {
+        r#"{"type":"object","properties":{"message":{"type":"string"}},"required":["message"]}"#.to_string()
+    }
+
+    fn description() -> String {
+        "Test tool for PTC: calls echo via tool_invoke".to_string()
+    }
+}
+
+fn execute_inner(params: &str) -> Result<String, String> {
+    let parsed: serde_json::Value = serde_json::from_str(params)
+        .map_err(|e| format!("Invalid params: {}", e))?;
+
+    let message = parsed.get("message")
+        .and_then(|v| v.as_str())
+        .ok_or("Missing 'message' parameter")?;
+
+    // Build the parameters for the echo tool
+    let echo_params = serde_json::json!({"message": message});
+
+    // Call tool_invoke with alias "echo_alias" which should resolve to "echo"
+    let result = near::agent::host::tool_invoke(
+        "echo_alias",
+        &echo_params.to_string(),
+    )?;
+
+    // Prefix to prove it went through WASM
+    Ok(format!("via_wasm:{}", result))
+}
+
+export!(TestPtcTool);