Finish axios migration via shared native HTTP helper

Replace all in-scope axios callsites with a new helpers/http.js wrapper over native fetch, including JSON/text GET, JSON POST, HEAD checks, and transient 5xx retry behavior; update all browser, build, script, and proxy API clients to use it; add focused unit tests; and remove axios from package dependencies.

Constraint: Preserve API/build and deployment behavior while lowering transport surface area.

Rejected: inline fetch replacements at each callsite | rejected to avoid inconsistent error/retry semantics.

Confidence: high

Scope-risk: moderate

Directive: Keep helper in place as the transport boundary and update tests when changing request semantics.

Tested: pnpm run -s typecheck, pnpm -s run test-prebuild, pnpm -s run test, pnpm -s run test:browser, pnpm -s run netlify-build, smoke GETs on /apple-silicon-app-test and /apple-silicon-app-test/?version=2

Not-tested: branch/netlify deployment health in CI pipeline after merge

test/prebuild/http.test.ts

@@ -0,0 +1,170 @@
+import {
+    afterEach,
+    beforeEach,
+    describe,
+    expect,
+    it,
+    vi
+} from 'vitest'
+
+import {
+    getJson,
+    getText,
+    headOk,
+    postJson,
+    requestJson,
+    shouldRetryError
+} from '~/helpers/http.js'
+
+describe( 'http helper', () => {
+    const fetchMock = vi.fn()
+
+    beforeEach( () => {
+        vi.stubGlobal( 'fetch', fetchMock )
+    } )
+
+    afterEach( () => {
+        vi.unstubAllGlobals()
+        vi.restoreAllMocks()
+        fetchMock.mockReset()
+    } )
+
+    it( 'retries transient 5xx errors and eventually resolves JSON', async () => {
+        fetchMock
+            .mockResolvedValueOnce( new Response( JSON.stringify({
+                ok: false
+            }), {
+                headers: {
+                    'Content-Type': 'application/json'
+                },
+                status: 502
+            } ) )
+            .mockResolvedValueOnce( new Response( JSON.stringify({
+                ok: true
+            }), {
+                headers: {
+                    'Content-Type': 'application/json'
+                },
+                status: 200
+            } ) )
+
+        await expect( getJson( 'https://api.doesitarm.com/sitemap-endpoints.json', {
+            attempts: 2,
+            delayMs: 0
+        } ) ).resolves.toEqual({
+            ok: true
+        } )
+
+        expect( fetchMock ).toHaveBeenCalledTimes( 2 )
+    } )
+
+    it( 'does not retry non-5xx errors', async () => {
+        fetchMock.mockResolvedValueOnce( new Response( JSON.stringify({
+            ok: false
+        }), {
+            headers: {
+                'Content-Type': 'application/json'
+            },
+            status: 404
+        } ) )
+
+        await expect( getJson( 'https://api.doesitarm.com/sitemap-endpoints.json', {
+            attempts: 3,
+            delayMs: 0
+        } ) ).rejects.toMatchObject({
+            response: {
+                status: 404
+            }
+        })
+
+        expect( fetchMock ).toHaveBeenCalledTimes( 1 )
+    } )
+
+    it( 'returns text responses', async () => {
+        fetchMock.mockResolvedValueOnce( new Response( '<xml />', {
+            headers: {
+                'Content-Type': 'application/xml'
+            },
+            status: 200
+        } ) )
+
+        await expect( getText( 'https://doesitarm.com/sitemap.xml' ) ).resolves.toBe( '<xml />' )
+    } )
+
+    it( 'posts JSON payloads and parses JSON responses', async () => {
+        fetchMock.mockResolvedValueOnce( new Response( JSON.stringify({
+            supportedVersionNumber: '2.1.0'
+        }), {
+            headers: {
+                'Content-Type': 'application/json'
+            },
+            status: 200
+        } ) )
+
+        await expect( postJson( 'https://doesitarm.com/api/test-results', {
+            filename: 'App.zip'
+        } ) ).resolves.toEqual({
+            supportedVersionNumber: '2.1.0'
+        } )
+
+        expect( fetchMock ).toHaveBeenCalledWith(
+            'https://doesitarm.com/api/test-results',
+            expect.objectContaining({
+                body: JSON.stringify({
+                    filename: 'App.zip'
+                }),
+                method: 'POST'
+            })
+        )
+    } )
+
+    it( 'supports config-object JSON requests for the API client', async () => {
+        fetchMock.mockResolvedValueOnce( new Response( JSON.stringify({
+            ok: true
+        }), {
+            headers: {
+                'Content-Type': 'application/json'
+            },
+            status: 200
+        } ) )
+
+        await expect( requestJson({
+            method: 'GET',
+            url: 'https://doesitarm.com/api/app/spotify.json'
+        }) ).resolves.toEqual({
+            ok: true
+        } )
+    } )
+
+    it( 'maps head requests to booleans', async () => {
+        fetchMock
+            .mockResolvedValueOnce( new Response( null, {
+                status: 200
+            } ) )
+            .mockResolvedValueOnce( new Response( null, {
+                status: 404
+            } ) )
+
+        await expect( headOk( 'https://doesitarm.com/sitemap.xml' ) ).resolves.toBe( true )
+        await expect( headOk( 'https://doesitarm.com/missing.xml' ) ).resolves.toBe( false )
+    } )
+
+    it( 'classifies retryable errors by HTTP status', () => {
+        expect( shouldRetryError( {
+            response: {
+                status: 502
+            }
+        } ) ).toBe( true )
+        expect( shouldRetryError( {
+            response: {
+                status: 503
+            }
+        } ) ).toBe( true )
+        expect( shouldRetryError( {
+            response: {
+                status: 404
+            }
+        } ) ).toBe( false )
+        expect( shouldRetryError( new Error( 'network' ) ) ).toBe( false )
+    } )
+} )