feat(providers): add Microsoft 365 Copilot individual provider

[skyzea1]

Summary

Fresh focused PR replacing #5287 as requested by the maintainer. This branch is based on release/v3.8.40 and keeps the diff limited to the Microsoft 365 Copilot individual web provider, registry/wiring, focused tests, and generated count/reference docs.

Scope

• Add copilot-m365-web / m365copilot provider and executor wiring.
• Add Microsoft 365 Copilot WebSocket executor support for the individual m365.cloud.microsoft/chat path.
• Keep credentials/operator session values external; no credentials are hardcoded.
• Mark account/session/request/location-specific validation details as redacted.
• Apply Rule fix(ui): fix Select dropdown dark theme inconsistency #12 fix: SSE abort paths sanitize WebSocket/startup error messages with sanitizeErrorMessage(...).
• Apply Rule fix(ci): add environment for npm token access #18 coverage: add executor unit test with a mock WebSocket covering handshake, OpenAI SSE chunking, incremental delta handling, finish lifecycle, and sanitized abort output.
• Update provider reference and live count docs for 237 providers / 68 executors.

Sanitized Validation Notes

All credentials, account identifiers, tenant/user-specific Chathub path values, session identifiers, request identifiers, and location-specific values are marked as redacted.

• Browser validation source: https://m365.cloud.microsoft/chat
• Access token: redacted
• Chathub path: redacted
• Account/session/request/location identifiers: redacted
• Observed protocol: SignalR WebSocket via Microsoft 365 Copilot Chathub
• Prompt used for live validation: Reply with exactly one word: pong
• Result: pong

Tests

npm exec -- tsx --import ./open-sse/utils/setupPolyfill.ts --test tests/unit/m365-connection-4042.test.ts tests/unit/m365-bizchat-frames-4042.test.ts tests/unit/copilot-m365-web-executor.test.ts
# 25/25 passing

npm run check:provider-consistency
# OK - 172 REGISTRY entries, 243 canonical providers

npm run check:docs-counts
# All checks pass

Related/reference PR: #5287

[gemini-code-assist]

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