feat(web): add inspectable and controllable OpenPI capability panels

[sowen1023]

Parent

• [Roadmap] OpenPI Web：像 Codex / Kimi Code 一样的本地浏览器 Agent 工作台 #76

Problem

The first Web workbench projects compact status summaries for Subagents, Workflows, and Background Terminals. The browser cannot inspect their full bounded evidence, understand dependency/state transitions, or invoke supported lifecycle controls. Tasks/Goals have no Web projection yet.

This limits the workbench to passive status badges for the OpenPI capabilities that most need long-running operational visibility.

Value

• Give operators one place to inspect delegated and background work.
• Expose exact progress and terminal evidence without copying capability logic into the browser.
• Allow supported stop/cancel actions through the capability owner.

Approach constraints

• Existing capability registries and lifecycle events remain authoritative.
• The browser consumes stable projections; it must not reconstruct completion from labels.
• Controls are exposed only where the owning capability already has exact semantics and authority checks.
• Every action binds resource identity, Session identity, controller lease, and current epoch.
• Logs, graphs, node lists, results, and retained resources require explicit size and retention bounds.
• Tasks/Goals must follow their accepted Pi/OpenPI lifecycle design rather than introducing a Web-only task system.

Acceptance criteria

• Subagent panels show identity, role/model when available, status, elapsed time, bounded progress, result, and cancellation evidence.
• Workflow panels show graph/node state, dependencies, bounded input/output evidence, failure, replay/provenance, and terminal result.
• Background Terminal panels show command identity, bounded output, readiness, exit/cancel state, and supported stop controls.
• Supported lifecycle commands return exact accepted/stale/settled/failed receipts and are idempotent.
• Tasks/Goals appear only after their canonical runtime contract exists, using the same projection boundary.
• Snapshot, SSE replay, reconnect, Session switch, and shutdown converge without ghost resources.
• Capability details remain bounded and provide recovery references for omitted evidence.
• Read-only viewers cannot invoke controller actions.
• Focused registry/protocol/UI/browser tests, bun run check, and bun run test pass.

Related work

• Todo 没有消失，只是被降级了：Codex 的 Plan / Goal / Evidence 演进，以及 OpenPI Tasks 应该怎么走 #43 tracks the broader Tasks design.
• control: 研究 Pi-native 的全局安全暂停，让所有 Agent 在下一执行边界停住 #161 tracks global safe pause semantics.
• docs(lifecycle): define background ownership, isolation, cancellation, settlement, and delivery #196 tracks cross-capability lifecycle ownership and cancellation documentation.

Out of scope

• A second orchestration runtime.
• Browser-owned task/workflow state.
• Recursive team management.