test(integration): add bootstrap flow tests via notstrap::run()

Three tests covering the full bootstrap path: dot-hook execution with
symlink verification, setup-hook skip-on-rerun via state file, and
fail-fast behaviour when the age key is missing.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/integration/Cargo.toml

@@ -6,8 +6,8 @@ license.workspace = true
 publish = false
 
 [[test]]
-name = "placeholder"
-path = "tests/placeholder.rs"
+name = "bootstrap"
+path = "tests/bootstrap.rs"
 
 [dev-dependencies]
 notstrap  = { path = "../../crates/notstrap" }