fix: add JSDoc Readonly type annotations for constant objects

Added proper JSDoc type annotations to VIEW_STATES, RUNTIME_STATES, and
LOADING_PHASES to preserve literal type information. This ensures TypeScript
recognizes the constant values as their specific literal types ('error', 'idle',
etc.) rather than generic strings.

Also replaced magic string 'idle' with RUNTIME_STATES.IDLE constant in
errors.js RETRY transition for consistency.

Fixes all type checking errors for state constant usage across transitions.

Author: deepdevjose

src/js/types.js

@@ -77,6 +77,14 @@
 /**
  * Constants for ViewState values
  * Must be synchronized with state-machine.js ViewState typedef
+ * @type {Readonly<{
+ *   WELCOME: 'welcome',
+ *   PERMISSION: 'permission',
+ *   LOADING: 'loading',
+ *   RUNTIME: 'runtime',
+ *   ERROR: 'error',
+ *   IMAGE_UPLOAD: 'image-upload'
+ * }>}
  */
 export const VIEW_STATES = {
     WELCOME: 'welcome',
@@ -89,6 +97,14 @@ export const VIEW_STATES = {
 
 /**
  * Constants for RuntimeState values
+ * @type {Readonly<{
+ *   IDLE: 'idle',
+ *   WARMING: 'warming',
+ *   RUNNING: 'running',
+ *   PAUSED: 'paused',
+ *   RECOVERING: 'recovering',
+ *   FAILED: 'failed'
+ * }>}
  */
 export const RUNTIME_STATES = {
     IDLE: 'idle',
@@ -101,6 +117,12 @@ export const RUNTIME_STATES = {
 
 /**
  * Constants for LoadingPhase values
+ * @type {Readonly<{
+ *   LOADING_MODEL: 'loading-model',
+ *   LOADING_WGPU: 'loading-wgpu',
+ *   WARMING_UP: 'warming-up',
+ *   COMPLETE: 'complete'
+ * }>}
  */
 export const LOADING_PHASES = {
     LOADING_MODEL: 'loading-model',

src/js/utils/transitions/errors.js

@@ -64,7 +64,7 @@ export const errorTransitions = [
         /** @this {import('../state-machine.js').default} */
         action: function () {
             this.state.error = null;
-            this.state.runtimeState = 'idle';
+            this.state.runtimeState = RUNTIME_STATES.IDLE;
         },
     },
 ];