Add dedicated environment settings page and test-in-environment (#4798)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies
> - Agents run inside environments (local, SSH, E2B sandbox)
> - Operators need to configure and manage these environments
> - But environment settings were buried inside the general company
settings page, making them hard to find
> - Additionally, when testing an agent from the configuration form, the
test always ran locally regardless of which environment was selected
> - This PR moves environments into a dedicated top-level company
settings section and wires the "Test Environment" button to run inside
the selected environment
> - The benefit is operators can find and manage environments more
easily, and the test button now validates the actual environment the
agent will use

## What Changed

- Added a dedicated `CompanyEnvironments` settings page with its own
route and sidebar entry
- Updated `CompanySettingsSidebar` and `CompanySettingsNav` to include
the new environments section
- Modified the agent test route (`POST /agents/:id/test`) to accept an
optional `environmentId` parameter
- Updated all adapter `test.ts` handlers to resolve and use the
specified execution target environment
- Added `resolveTestExecutionTarget` to `execution-target.ts` for remote
environment test resolution with cwd fallback
- Moved the "Test Environment" button and its feedback display into the
`NewAgent` page footer for better UX flow

## Verification

- `pnpm test` — all existing and new tests pass
- `pnpm typecheck` — clean
- Manual: navigate to Company Settings, confirm "Environments" appears
as a top-level section
- Manual: configure an agent with a non-local environment, click "Test
Environment", confirm the test runs inside that environment

## Risks

- Low risk. UI-only routing change for the settings page. The
test-in-environment change adds an optional parameter with a local
fallback, so existing behavior is preserved when no environment is
specified.

## Model Used

Codex GPT 5.4 high via Paperclip.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] If this change affects the UI, I have included before/after
screenshots
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

ui/src/api/agents.ts

@@ -175,7 +175,10 @@ export const agentsApi = {
   testEnvironment: (
     companyId: string,
     type: string,
-    data: { adapterConfig: Record<string, unknown> },
+    data: {
+      adapterConfig: Record<string, unknown>;
+      environmentId?: string | null;
+    },
   ) =>
     api.post<AdapterEnvironmentTestResult>(
       `/companies/${companyId}/adapters/${type}/test-environment`,