Clarify HTTP MCP setup in Settings (codex)

[numnx]

🧩 Task: Clarify HTTP MCP setup in Settings

Automated task PR opened by Code UX for T03.

📋 Summary

Sprint: Sprint 139 · Settings mcp and & custom container · Task: T03

Improve Settings so operators can configure HTTP MCP servers with clear guidance and choose a custom container setup script through a file-picker field.

📝 Full Task Prompt

## Objective
Improve the MCP Settings page so users can understand how to configure Code UX and custom servers over HTTP/SSE MCP without leaving the panel.

## Scope
- `dashboard/src/v2/components/settings/panels/SettingsMcpPanel.tsx`
- `tests/dashboard/v2/settings-mcp-panel.test.tsx` or an adjacent focused dashboard test file
- `docs/mcp/runtime-and-dispatch.md`
- `docs/dashboard/design-system-settings.md`
- `docs/index.md` and `docs/SUMMARY.md` only if a new dedicated docs page is created; otherwise leave links in place

## Implementation Requirements
1. Add a concise guidance section to `SettingsMcpPanel.tsx` explaining that Code UX exposes MCP over stdio by default and optional authenticated Streamable HTTP via `MCP_HTTP_*` env vars or `--mcp-http*` flags.
2. In the custom server detail view, make HTTP/SSE setup clearer by showing when to choose `HTTP / SSE`, where to paste the server URL, how optional auth headers are represented as JSON, and that changes are injected on the next CLI run.
3. Keep the generated config preview accurate for HTTP servers with `{ type: "http", url, headers }` and for stdio servers with command/args/env; do not change persisted custom server shape unless tests prove an existing field is wrong.
4. Add focused dashboard tests that render the MCP panel, open or create a custom MCP server, select HTTP transport, and assert the setup guidance, URL field, auth headers field, and preview are visible and accessible.
5. Update `docs/mcp/runtime-and-dispatch.md` with the same Settings-page HTTP setup path and update `docs/dashboard/design-system-settings.md` with any new MCP panel UI/accessibility expectations.

## Constraints
- Do not implement new MCP transport behavior; this task is UX/documentation for existing stdio and HTTP runtime support.
- Do not rename the MCP category or move MCP settings into another panel.
- Do not expose secrets in previews beyond the user-entered header JSON already present in the draft.
- Preserve project/system scope behavior: custom servers are added at system scope and can be enabled, disabled, or overridden at project scope.

## Verification
- Run `pnpm exec vitest run tests/dashboard/v2/settings-mcp-panel.test.tsx` or the focused test file created for this task.
- Run `pnpm run test:dashboard`.
- Run `pnpm run lint`.
- Success means the MCP panel explains HTTP setup, HTTP server fields remain editable, previews stay accurate, and dashboard tests pass.

✅ QA Review

⏳ QA review runs after this PR is opened. Check the task card in the dashboard for the outcome once it lands.

🤖 Model & Provider

Provider	Codex CLI
Model	gpt-5.5

⏱️ Timing

Started	2026-07-06 09:48:48 UTC
Finished	2026-07-06 09:54:01 UTC
Duration	5m 13s

📊 Token Usage

Metric	Value
Input tokens	99,625
Cached input tokens	1,657,472
Output tokens	8,907
Total tokens	1,766,004
Invocations	1
Tool calls	47
Active time	4m 35s

Included usage estimate (subscription/local login): $1.59

🌿 Branch Info

Base: feature/CODUX-139-settings-mcp-and-custom-container
Head: task/feature-codux-139-settings-mcp-and-custom-contai-t03-codex-mr91fgh5

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🤖 Generated by Code UX