feat(cc-config): add and remove MCP servers through the claude CLI

Mutation goes through `claude mcp add|remove`, never a direct edit of
~/.claude.json — the running CLI rewrites that file concurrently, so a
dashboard write would race it. Reads stay on readMcpServers.

The plan specified a --url flag; the real CLI (v2.1.266) has none —
commandOrUrl is positional, and --header must trail it or the variadic
flag swallows the url. Built against the verified shape.

docs/API.md

@@ -1560,7 +1560,7 @@ curl "http://localhost:4820/api/sessions?sources=local,4d1f0e2a-7b9c-4c33-8a21-9
 
 ### Claude Config Explorer
 
-The `/api/cc-config/*` namespace powers the Claude Config Explorer, now the **Claude Code** tab of Settings (`/settings?tool=claude-code`). All read endpoints are pure file reads under `CLAUDE_HOME` and the project's `.claude/` dir. File mutations cover the low-risk text-file artifacts (skills, subagents, slash commands, output styles, memory), `keybindings.json`, and `settings.json` layers **via a per-key merge only** — each always creates a timestamped backup before writing. Plugin and marketplace management is delegated to the `claude plugin …` CLI. MCP server config stays read-only, because it is written concurrently by the running Claude Code CLI.
+The `/api/cc-config/*` namespace powers the Claude Config Explorer, now the **Claude Code** tab of Settings (`/settings?tool=claude-code`). All read endpoints are pure file reads under `CLAUDE_HOME` and the project's `.claude/` dir. File mutations cover the low-risk text-file artifacts (skills, subagents, slash commands, output styles, memory), `keybindings.json`, and `settings.json` layers **via a per-key merge only** — each always creates a timestamped backup before writing. Plugin/marketplace management and MCP server add/remove are delegated to the `claude plugin …` / `claude mcp …` CLI, because `~/.claude.json` and the plugin manifests are rewritten concurrently by the running Claude Code CLI.
 
 ```http
 GET /api/cc-config/overview
@@ -1593,6 +1593,8 @@ POST /api/cc-config/plugins/install       Body: { spec, scope? }
 POST /api/cc-config/plugins/action        Body: { key, action: enable|disable|update|uninstall }
 POST /api/cc-config/marketplaces/add      Body: { source, scope? }
 POST /api/cc-config/marketplaces/action   Body: { name, action: update|remove }
+POST /api/cc-config/mcp/add               Body: { name, scope, transport?, url?, headers?, command?, args?, env? }
+POST /api/cc-config/mcp/remove            Body: { name, scope? }
 ```
 
 `scope` is `"user"`, `"project"`, or `"auto-memory"`. `type` is one of `skills`, `agents`, `commands`, `output-styles`, `memory`, `auto-memory`. `name` is required for everything except `memory` (which is `CLAUDE.md` itself). On `PUT`, `name` is validated against `^[A-Za-z0-9][A-Za-z0-9._-]{0,63}$` (for `auto-memory` it must instead be a flat `*.md` filename). Settings are returned with secret-like keys (matching `/token|secret|password|api[_-]?key|auth/i`) replaced by `"<redacted>"`.
@@ -1605,6 +1607,8 @@ POST /api/cc-config/marketplaces/action   Body: { name, action: update|remove }
 
 **Plugins and marketplaces.** These five endpoints shell out to the `claude plugin …` CLI with an explicit argv array (never a shell string), pinned to the dashboard's `CLAUDE_HOME` via `CLAUDE_CONFIG_DIR`; mutating calls are serialized in-process. `source` must be `owner/repo`, an `http(s)://` URL, or an absolute path; `spec`/`key` must be `<name>` or `<name>@<marketplace>`; `scope` is `user` (default), `project` or `local`. Validation failures return 400 `EBADARG`; a missing `claude` binary returns 503 `ECLINOTFOUND`; a CLI timeout returns 504 `ETIMEOUT`; a non-zero CLI exit returns **422 `ECLIEXIT`** with the CLI's message plus `stdout`/`stderr`. Successful runs return `{ ok: true, stdout, stderr }` and broadcast `cc_config_changed`. `GET /plugins/available` proxies `claude plugin list --available --json` as `{ installed, available }`.
 
+**MCP servers.** `POST /api/cc-config/mcp/add` and `POST /api/cc-config/mcp/remove` shell out to `claude mcp add`/`claude mcp remove` the same way the plugin routes shell out to `claude plugin …` — an argv array, never a shell string, serialized in-process. `scope` is `user` or `project` only (required on add, optional on remove — omitted, the CLI removes from whichever scope the server exists in); the settings union's third value `project-local` is a different axis and is not accepted here. `add` takes either `url` (+ optional `transport: "http"|"sse"`, `headers`) for a remote server, or `command` + `args` (+ optional `env`) for a stdio server — exactly one of the two forms. Validation failures return 400 `EBADARG`; a non-zero CLI exit returns 422 `ECLIEXIT`. `GET /api/cc-config/mcp` is unaffected — it still reads `~/.claude.json` directly; the client refetches it after either call succeeds.
+
 `PUT /api/cc-config/keybindings` edits `~/.claude/keybindings.json` from a structured list of context groups (`{ groups: [{ context, bindings: [{ key, action }] }] }`). The server backs the file up first (under `<CLAUDE_HOME>/cc-config-backups/keybindings/`), preserves any top-level metadata (`$schema`/`$docs`), and replaces only the `bindings` array; duplicate contexts or duplicate keys within a context return `EBADCONTENT`. `keybindings.json` is replaced wholesale here because the live CLI does not rewrite it mid-session; `settings.json`, which it does, is only ever key-merged (see `PATCH /settings` above).
 
 **Auth profiles (`/profiles*`).** A *profile* is one Anthropic account — one quota — under a name. Switching swaps exactly two identity artifacts and nothing else: `claudeAiOauth` inside `<CLAUDE_HOME>/.credentials.json`, and `oauthAccount` + `userID` inside the `.claude.json` config file(s) (`<CLAUDE_HOME>.json` and `<CLAUDE_HOME>/.claude.json`, each rewritten only if it already exists, key-merged so `projects`/`numStartups`/everything else survives). Skills, subagents, commands, memory, plugins, marketplaces, MCP servers and settings are never read or written here — that is what makes a switch keep the whole workspace and change only the account. `mcpOAuth` also stays put: those are the machine's MCP server tokens, not account identity.