feat(gateway): add native Fluxer platform adapter

[kaitwalla]

Summary

• add a native bundled Fluxer messaging plugin using Fluxer REST and Gateway APIs
• support DMs and server channels, replies, typing, edits, reactions, uploads, reconnect/resume, home-channel delivery, allowlists, and pairing ingress
• add guided setup, environment/config documentation, and self-hosted endpoint support
• repair bundled-platform contract discovery so those contracts execute instead of silently receiving an empty parameter set

Security and isolation

• require HTTPS/WSS for remote endpoints; plaintext HTTP/WS is limited to loopback development
• validate configured, discovered, and resume Gateway URLs before credentials are transmitted
• reject endpoint userinfo, query strings, fragments, malformed authorities, and invalid ports
• download inbound attachments only after authorization returns exactly True; unknown text still reaches central pairing
• bound outbound file reads and run filesystem reads off the event loop
• use token-scoped platform locks without exposing credentials, including shared --replace takeover semantics
• preserve per-profile credentials, allowlists, sessions, and home-channel configuration

Verification

• 67 passed — focused Fluxer unit/setup/in-process REST+WebSocket integration suite
• 793 passed — selected platform/config/session contracts, 0 skipped
• Ruff format/check passed
• ty passed
• staged credential scan passed
• independent hash-pinned security/correctness review passed with no blocking findings
• complete Gateway run: 11,571 passed, 21 failed, 4 skipped; no Fluxer tests failed. The 21 unrelated failures were rerun by file: 20 passed, and the remaining busy-ack test passed with an isolated HERMES_HOME (the live profile had busy_ack_detail enabled).

Notes

The adapter talks to Fluxer natively; it does not redirect or impersonate the Discord adapter. Self-hosted REST bases are full versioned URLs such as https://chat.example.com/api/v1.

[teknium1]

Thank you for the substantial adapter implementation and the focused gateway coverage.

Problems

• The new bundled integration at plugins/platforms/fluxer/plugin.yaml:1 conflicts with the standing policy at AGENTS.md:797-810: new third-party-product plugins must ship as standalone plugin repositories rather than new directories under plugins/.
• This PR also contains a separately valid current-main repair. tests/gateway/test_plugin_platform_interface.py:17-18 builds tests/plugins/platforms, not the repository's plugins/platforms; its dynamic platform parameter set therefore does not cover bundled adapters.

Suggested changes

• Publish Fluxer as a standalone platform plugin using the existing ctx.register_platform() surface, which current docs identify for user-installed third-party platform adapters (website/docs/user-guide/features/plugins.md:180,230).
• Keep the PROJECT_ROOT correction as a focused contract-test change so the existing bundled-platform checks actually execute.

This is an automated hermes-sweeper review.

[teknium1]

This creates a new in-tree third-party product integration. AGENTS.md:797-810 requires such plugins to ship as standalone repositories installable under ~/.hermes/plugins/; please move the Fluxer adapter to that extension path rather than adding it under plugins/.

[kaitwalla]

Superseded by the standalone plugin repository requested in review:

• https://github.com/kaitwalla/hermes-fluxer
• Install: hermes plugins install kaitwalla/hermes-fluxer --enable
• Guided setup: hermes fluxer setup

The unrelated bundled-platform contract-test correction is now isolated in #74953. Closing this monorepo integration PR in favor of those two focused deliverables.