docs: record the Result-handling convention

CLAUDE.md

@@ -46,3 +46,9 @@ src/
 - Ports & Adapters: interfaces in `domain/ports/`, implementations in `infrastructure/adapters/`
 - External libraries (clack, picocolors) only in `infrastructure/`
 - Exception: valibot in `domain/schemas/` (declarative type definitions)
+
+### Result handling
+
+- Every `Result` from a port call must be checked (`.success` / `Result.isOk` / `Result.isErr`) before the code moves on
+- A deliberately discarded `Result` is marked with `// ignored: <reason>` so review can tell intent from oversight
+- Mechanical enforcement was considered and deferred: Biome 2.x GritQL has no type information, so a syntactic rule would need a hand-maintained list of ~42 port method names, and a second type-aware linter is disproportionate for a bug class with no live instances

src/cli/commands/create.ts

@@ -127,6 +127,8 @@ export function createCommand(container: Container) {
 
 				const cleanup = new CleanupHandle();
 				cleanup.register(async () => {
+					// ignored: best-effort rollback on an already-failing path — a failed cleanup
+					// has no useful handling and must not mask the original error
 					await git.removeWorktree(createResult.data.worktree.path, { force: true });
 				});