Modernize hosted MCP boundaries for 2026-07-28

[dajiaohuang]

Summary

• add dual-era MCP SDK v2 Host/client support across stdio, SSE, Streamable HTTP and the in-process bridge, with deterministic modern catalogs and explicit legacy fallback
• preserve standard MCP text, image, audio, resource and embedded-resource results while producing bounded HostMediaEnvelope artifacts for Web delivery
• separate trusted campaign/identity/authorization data from player text, sign dedicated audience-scoped auth-context v2 delegations, propagate trace context and reject token passthrough
• connect only the active campaign system in Hosted mode, bound parallel connection setup, reuse HTTP clients and export low-cardinality MCP phase metrics
• add registered-workspace TTL/capacity/LRU cleanup that never removes unknown, symlinked or active directories
• update English/Chinese operator docs and Local Kit templates

Compatibility

Boundary	Legacy	MCP 2026-07-28
stdio Client	initialize/session compatibility	per-request v2 Client mode
Streamable HTTP Client	explicit legacy mode	auto/modern without Mcp-Session-Id authority
Hosted Worker	v1 fallback for older domains	auth-context v2, request-scoped identity/revision/expiry
Host bridge server	legacy downstream default during rollout	dual-era upstream; modern downstream configurable

The v2 delegation wire contract is aligned to merged Sagasmith-core commit 0ac316655687757203a9df1b2eb81669ec1d2d78. No component lock is changed here; the coordinated lock update should follow merged domain-server commits.

Validation

• uv run pytest -q: 5357 passed, 71 skipped, 132 warnings in 292.29s
• real domain conformance: 7 passed, 35 skipped in 118.26s
• Feishu suite: 43 passed
• final affected MCP/Hosted suite: 162 passed, 2 skipped in 22.32s
• uv run ruff check .: passed
• NANOBOT_SKIP_WEBUI_BUILD=1 uv build: sdist and wheel built

No production data, paid model or external service was used. Rollback can select protocolMode legacy while retaining the request-scoped identity boundary; the legacy bridge is compatibility-only and must not become the long-term authority model.