test: build binary automatically via TestMain

Removes the need to run 'go build' before 'go test' by building the
binary in TestMain and cleaning it up after tests complete.

This makes the test suite self-contained and simplifies both the
README instructions and the GitHub Actions workflow.

Also ensures Procfile.dev is cleaned up after integration tests and
added to .gitignore as a fallback.

#1

Co-authored-by: Warp <agent@warp.dev>

Author: croaky

.github/workflows/test.yml

@@ -17,8 +17,5 @@ jobs:
         with:
           go-version: "1.25"
 
-      - name: build
-        run: go build -v -o procman .
-
       - name: test
         run: go test -v ./...

.gitignore

@@ -1 +1,2 @@
 procman
+Procfile.dev

README.md

@@ -69,7 +69,6 @@ for a PTY interface.
 ## Developing
 
 ```bash
-go build ./...                        # build
 go test ./...                         # run tests
 go vet ./...                          # static checks
 goimports -local "$(go list -m)" -w . # format imports

procman_test.go

@@ -9,6 +9,18 @@ import (
 	"time"
 )
 
+func TestMain(m *testing.M) {
+	cmd := exec.Command("go", "build", "-o", "procman", ".")
+	if err := cmd.Run(); err != nil {
+		fmt.Fprintf(os.Stderr, "failed to build: %v\n", err)
+		os.Exit(1)
+	}
+	code := m.Run()
+	os.Remove("procman")
+	os.Remove("Procfile.dev")
+	os.Exit(code)
+}
+
 func TestSetupProcesses(t *testing.T) {
 	tests := []struct {
 		name      string
@@ -134,7 +146,6 @@ func TestWriteErr(t *testing.T) {
 }
 
 // TestProcmanIntegration tests the full procman workflow.
-// Requires `go build -o procman .` to be run first.
 func TestProcmanIntegration(t *testing.T) {
 	content := "echo: echo 'hello'\nsleep: sleep 10"
 	if err := os.WriteFile("Procfile.dev", []byte(content), 0644); err != nil {