test: isolate validation from local model services

[jonathanKingston]

Summary

• prevent the remote-agent fallback unit test from probing a developer's LM Studio instance
• inject the missing category classifier in the roadmap import fallback test so background work remains hermetic
• seed E2E profiles with an unreachable local model URL by default while preserving explicit fixture overrides

Validation

• pnpm test -- agent-service roadmap-issue-import provider-selection (93 tests passed with LM Studio running locally)
• pnpm run check:e2e-syntax (268 files parsed)
• pnpm run check (8,547 tests passed on the combined validated changeset)

[copse-release-bot]

Reference screenshots ready for review

Review GitHub’s image diffs in screenshot PR #2414.
Merge it (or enable auto-merge) to apply the accepted PNGs to codex/isolate-tests-from-local-model.

Rendered for ff5f8e6322e6 by CI run 34024329514; the immutable artifact is reference-screenshot-candidates-34024329514.

If this source branch moves, a later successful render closes the stale review PR and replaces this link.

[jonathanKingston]

Validation follow-up (2026-09-05): re-reviewed the isolation boundaries. The unit-test environment override is restored in finally; the E2E default remains overrideable by fixtures through the supported settings surface; and the missing category classifier removes the uncontrolled background provider path. The PR is mergeable, check is green, and all eight E2E shards passed. No further source changes needed.

[github-actions]

🖥️ PR preview

• Marketing site
• Browser demo
  Interactive, with a mocked backend — jump to a scenario:
• Builds a cupcake site
• Agent-proposed edits open the Changes panel
• Markdown list indentation
• Responsive composer footer
• Subagent display visual reference
• Subagent stays ungrouped beside reading tools
• Semantic search subagent markdown
• Light-theme approval with a bright accent
• Grouped outside-sandbox command approval
• Remote desktop discovered-port list with one selected
• Settings scroll + sticky footer geometry
• Per-model reasoning / temperature / top-p
• Thread switch hydration notice
• Thread switch hydration failure
• Chat layout styling
  _{Static demo of the renderer against a mock API — the browser pane, terminal, and all main-process IPC are stubbed, so it never proves main-process behaviour. Rebuilt whenever a push changes the demo bundle; these links go live once the queued deploy lands, shortly after this comment. Removed when the PR closes.}