feat(teams): graph primitive subpath + SSRF allowlist divergence (chat@4.31 8c71411) (#160)

Port the Microsoft Graph primitives subpath (NEW in chat@4.31.0) for the
Teams adapter as a runtime-free, SDK-free package mirroring slack/api and
teams/api: call_teams_graph_api (Graph .default scope), paginate_teams_graph
(follows @odata.nextLink as-is), get_teams_channel, list chat/channel
messages + replies, get_teams_channel_message, and the ordered
extract_text_from_graph_message HTML->text pass (entity-decode & last).

Reuses the Round-1 api subpath (resolve_teams_access_token,
read_response_body, TeamsApiError) via the allowed cross-subpath import.
Injectable async fetch (AsyncMock in tests) defaults to the api subpath's
lazy-httpx transport.

Python-first divergence: gate an absolute path_or_url and every followed
@odata.nextLink to the graph.microsoft.com host BEFORE attaching the Bearer
token (SSRF / token-leak guard), raising ValueError for any other host.
Upstream attaches the token to whatever URL it is handed.

Ports all 7 graph/index.test.ts it-blocks + the boundary source-scan, plus
direct text-extraction coverage, the nextLink-host SSRF rejection test, and
a no-eager-httpx import check.

Author: patrick-chinchill