fix(webui): label each MCP server's connection state on the plugin row (D-3)

[stevenjj33]

Change

Roadmap D-3（转述口径，fork 的 issues 已禁用、roadmap 在团队侧，仓内无 D-3 字样可核）: 「MCP 插件连不上时，界面上要看得见」.

Investigation first. The runtime already classifies every MCP server and puts it on the wire — LocalMcpPublicServerStatus (local-runtime-v2/src/service/mcp/contracts.ts) carries status: available | configured | disabled | error | unavailable plus the failure's own reason string on the two trouble states, produced by listPublicServerStatuses (runtimeErrors → error + reason; static prerequisites missing → unavailable + reason). The WebUI panel's MCP rows rendered none of it: the mcp area's row had only 编辑 / 删除 / 启用开关 — a server that could not connect was visually identical to a healthy one. (appStatus exists but is rendered only in the apps area.)

Fix — a status chip in the slot the apps area already uses, plus the reason as visible text:

• describeWebuiMcpServerStatus (exported pure function in PluginManagement.tsx): maps the row's loose status onto a labelled view — 已连接 / 未连接 / 已停用 for the calm states (configured is deliberately NOT trouble: enabled-and-resting is a server that connects on use), 连接失败 in the danger tone and 不可用 in the warning tone for the trouble states, each carrying the runtime's own reason (error / errorMessage keys).
• The reason renders inline as visible text — not a tooltip, because nobody hovers a row they believe is healthy — ellipsis-clamped with the full string on the element's title, so a long server error cannot push the 编辑/删除/开关 strip out of the row. Small CSS addition (.webui-plugin-mcp-status).
• Unknown / missing status → 未知状态 with no invented reason: the label claims nothing, and a reason under it would claim something the reader cannot verify.

Browser verification (built client, real Chromium, walked the real path): rail 插件 → 管理 → MCP tab with a staged listing covering all five states —

server	status	rendered	reason rendered
broken-http	error	连接失败	MCP_CONNECTION_TIMEOUT: 握手超时（10s） — inline, visible
gone-binary	unavailable	不可用	MCP_COMMAND_NOT_FOUND: ./missing-bin — inline, visible
ok-stdio	available	已连接	—
idle	configured	未连接	—
off	disabled	已停用	—

Before the change the same listing rendered no status text anywhere in the rows.

Validation

• pnpm test:webui — 83 files / 1653 tests passed, including new plugin-mcp-status.test.tsx (6 cases: per-state labels, reason passthrough for both trouble states incl. the errorMessage key, trouble tones ≠ neutral tone, unknown-claims-nothing, row-wiring source assertions).
• npx playwright test — 88/88 passed, including new plugin-mcp-status.spec.mjs (2 cases, harness-imported test: failure states labelled with their server's own reason via the real rail→管理→MCP path; calm states labelled so trouble has honest neighbours; no invented reasons).
• pnpm typecheck:webui-full, pnpm check:source (inventory regenerated), pnpm verify — passed, 20 gates on darwin.
• Fixture change is additive: setPluginManagementResult(action, result) keyed per action; default stays {}, existing specs untouched.

NOT RUN / boundaries

• The staged listing runs against the fixture transport; no real MCP server was crashed end-to-end (that needs a live pnpm dev:server session with a real failing server config). The status/reason fields consumed are the runtime's own contract, source-verified at listPublicServerStatuses.
• Scope note: visibility lives in the plugin panel (the plugins home). A rail-level badge on 插件 for ambient discovery would need shell-side MCP polling — out of scope here, worth a follow-up if wanted.

Publication and contribution checks

• I have permission to contribute these changes under the existing licenses applicable to the changed files/packages; imported material and its provenance are identified and existing notices are preserved.
• No credentials, account data, real user content, internal source history or private review material is included.
• Added/removed source files were reviewed before regenerating release/public-source.json; new tests are declared in test/vitest-suites.json where applicable.
• Shared English/Chinese documentation and capability/verification records are updated where applicable. Mock/offline results are not described as live-service acceptance.

Maintainer handoff

Publication scope or license changes (if any): none.

Shared-source port: not needed.