fix(test): isolate the web runner in a separate application scope (#3374)

[bpamiri]

Summary

The web test runner no longer mutates the live application.wheels when Application.cfc includes the shipped snippet. Test-runner URLs, TestClient, and browser specs bind a separate CFML application name (_wheelsTest) so concurrent normal requests keep production config.

This is the #3374 successor to #3025 / #3373. A request-scoped overlay remains infeasible (blockers B1–B9). Isolation is a second application context inside the same servlet — verified against those blockers rather than guessed.

Related Issue

Closes #3374

Type of Change

• Bug fix
• Enhancement to existing feature
• Documentation update

Approach (verified against B1–B9)

Changing this.name in Application.cfc's constructor is the only CFML mechanism that yields a separate application scope (own model/dialect caches, own routes, own datasource wiring). That sidesteps:

• B1–B3 — dialect adapter, column schema, and automaticValidations stay baked per isolated app; no StructClear(models) of the live cache
• B8–B9 — routes and path swaps live on the test application only
• B6 — browser / ParallelRunner / TestClient address the isolated context via path (/wheels/core/tests, /wheels/app/tests) or X-Wheels-Test-Context or WHEELS_TEST_CONTEXT cookie. Header (not URL prefix) is required for Playwright: in-page navigations and form posts would drop a prefix/query marker; extraHTTPHeaders persists across the context.

$get() overlay / tenant datasource reuse was re-checked and rejected: the tenant override swaps only the datasource name after dialect SQL is generated, and cannot re-bake adapters (B1).

What shipped

• vendor/wheels/events/testcontext.cfm — constructor include (no CFC new here: mappings are not guaranteed during Application.cfc construction)
• vendor/wheels/events/TestContext.cfc — runtime twin (same suffix / header / cookie); unit-testable
• Demo + wheels new + example Application.cfc include the snippet after config/app.cfm
• WheelsTest.$testClient() sends the header + cookie by default; $testClient(testContext=false) hits the live app. Local is named httpClient (not client) so Lucee does not throw "client scope is not enabled" (anti-pattern 11)
• BrowserTest sets Playwright extraHTTPHeaders + isolation cookie
• ParallelRunner partition GETs send the header (path already matches)
• fix(test): serialize web test-runner config swap under a named lock (#3025) #3373 named-lock swap remains as the fallback for apps that have not applied the include, and still serializes test-vs-test inside the isolated app
• Runner swap now set(loadBrowserTestFixtures=false) and clears controller / object-file caches so isolated-app boot does not leave controller("wheels") resolving to the browser-fixture Controller.cfc stub
• Interface specs instantiate controller("Test") (a real test-asset CFC) instead of the no-file wheels fallback
• Specs in vendor/wheels/tests/specs/internal/TestRunnerIsolationSpec.cfc
• Changelog fragment + MDX / .ai / CLAUDE.md updates
• tools/test-local.sh internal / interfaces map to the matching wheels.tests.specs.* directories

Leftovers (not papered over)

• Existing apps must add the Application.cfc include to opt in. Without it, behavior is unchanged (fix(test): serialize web test-runner config swap under a named lock (#3025) #3373 lock + live-scope swap).
• Per-datasource application names (_wheelsTest_sqlite) were deferred: browser requests have no ?db= and would bind a different app than the runner.
• Request-scoped overlay is still blocked by B1–B9 (not attempted).
• Legacy in-process $wheelsRunner (wheels.Test) still swaps if invoked; wheels test uses HTTP /wheels/core|app/tests and is isolated.
• First test request cold-starts the isolated application (onApplicationStart of the second name).

Feature Completeness Checklist

• DCO sign-off
• Tests — unit (path/header/cookie), structural (wiring), behavioral (live /wheels/info sees a different application name)
• Framework Docs — fixtures-and-test-data.mdx, running-tests-locally.mdx
• AI Reference Docs — .ai/wheels/testing/browser-testing.md
• CLAUDE.md — Testing Quick Reference
• Changelog fragment — changelog.d/test-runner-app-isolation.fixed.md

Test Plan

Local Lucee 7 + SQLite via tools/test-local.sh:

• internal — 92 passed (isolation + swap-lock + TestClient)
• interfaces — 57 passed
• full core suite — 4801 passed

Also verified over HTTP: /wheels/info?format=json returns wheels-dev; the same URL with X-Wheels-Test-Context: 1 or WHEELS_TEST_CONTEXT=1 returns wheels-dev_wheelsTest.