fix: nil-close bug, stale docs, dead code, and tracked binaries

- Fix potential nil file.Close() panic in devModePersist/devModeRemovePersisted
  by extracting loadDevModeMap/saveDevModeMap helpers with proper defer
- Remove tracked binaries (pathparams 10.8 MB, shake.db 22 MB) and consolidate
  .gitignore with a wildcard pattern covering all 19 examples
- Remove stale reaper reference in README (removed in dc56261), update example
  count from 14 to 19, fix OnChange debounce claim in docs
- Fix typos: "percist"→"persist", "percisted"→"persisted", "tmplates"→"templates"
- Remove dead code: commented import in signal_test.go, unnecessary fmt.Sprintf
  in computed.go, commented picocss imports and no-op Config calls in examples
- Replace go fmt with gofmt -l check in ci-check.sh to fail on unformatted code
  instead of silently reformatting

docs/state-and-interactivity.md

@@ -94,7 +94,7 @@ Available triggers:
 |--------|-------|-------|
 | `OnClick()` | `click` | |
 | `OnDblClick()` | `dblclick` | |
-| `OnChange()` | `change` | 200ms debounce |
+| `OnChange()` | `change` | |
 | `OnInput()` | `input` | No debounce |
 | `OnSubmit()` | `submit` | |
 | `OnKeyDown(key)` | `keydown` | Filtered by key name (e.g. `"Enter"`, `"Escape"`) |