feat(v0.3): add built-in project CLAUDE.md template

ClaudeMDProject returns the project-oriented default used when
--project is passed (and no project seed overrides it). Adds tests
asserting required v0.3 spec sections and ASCII-only content.

internal/seed/templates.go

@@ -39,6 +39,40 @@ Keep it concise -- a few bullet points is enough.
 `
 }
 
+// ClaudeMDProject returns the built-in default CLAUDE.md content for a project workspace.
+func ClaudeMDProject() string {
+	return `# Project Workspace Guidelines
+
+This is a ctask project workspace -- a long-lived working environment, not a disposable task.
+
+## File Placement
+
+- Source code -> ` + "`src/`" + ` or workspace root
+- Documentation -> ` + "`docs/`" + `
+- Deliverables and exports -> ` + "`output/`" + `
+- Reference material -> ` + "`context/`" + `
+- Tests -> ` + "`tests/`" + `
+- Configuration files -> workspace root
+- Do not place non-code outputs in the workspace root
+
+## Conventions
+
+- This project uses git. Commit meaningful changes with clear messages.
+- Do not install global packages or modify system files unless asked.
+- Record important assumptions and actions in notes.md.
+- Keep the workspace root clean.
+
+## Session Handoff
+
+Before ending a session, append a brief summary to notes.md with:
+
+- What was accomplished
+- Key decisions made
+- Open follow-ups or unfinished work
+- How to continue from here
+`
+}
+
 // NotesMD returns the skeleton notes.md content.
 func NotesMD(title string) string {
 	return fmt.Sprintf(`# %s

internal/seed/templates_test.go

@@ -34,6 +34,34 @@ func TestClaudeMDContainsV03Sections(t *testing.T) {
 	}
 }
 
+func TestClaudeMDProjectIsASCII(t *testing.T) {
+	content := ClaudeMDProject()
+	for i, b := range []byte(content) {
+		if b > 127 {
+			t.Errorf("non-ASCII byte 0x%02x at position %d in project CLAUDE.md template", b, i)
+			break
+		}
+	}
+}
+
+func TestClaudeMDProjectContainsRequiredSections(t *testing.T) {
+	content := ClaudeMDProject()
+	for _, want := range []string{
+		"# Project Workspace Guidelines",
+		"long-lived working environment",
+		"## File Placement",
+		"Source code -> ",
+		"Tests -> ",
+		"## Conventions",
+		"This project uses git",
+		"## Session Handoff",
+	} {
+		if !strings.Contains(content, want) {
+			t.Errorf("project CLAUDE.md missing required section: %q", want)
+		}
+	}
+}
+
 func TestNotesMDIsASCII(t *testing.T) {
 	content := NotesMD("test title")
 	for i, b := range []byte(content) {