What does this PR do?

Adds full support for ntfy as a messaging platform. ntfy is a lightweight, open-source push notification service that works with ntfy.sh or any self-hosted server.

Reopened from #4043 with all reviewer feedback addressed.

Type of Change

• New feature (non-breaking change which adds functionality)

Changes Made

• gateway/platforms/ntfy.py — platform adapter with HTTP streaming subscription, exponential backoff reconnection, message deduplication, Bearer/Basic auth support
• gateway/config.py — NTFY platform enum entry and env var loading (NTFY_TOPIC, NTFY_SERVER_URL, NTFY_TOKEN, NTFY_PUBLISH_TOPIC, NTFY_MARKDOWN)
• gateway/run.py — adapter factory and authorization maps
• cron/scheduler.py — ntfy delivery in platform map
• tools/send_message_tool.py — ntfy routing and _send_ntfy()
• toolsets.py — hermes-ntfy toolset and gateway composite
• hermes_cli/status.py — ntfy status display
• agent/prompt_builder.py — ntfy platform hint
• gateway/channel_directory.py — session-based channel discovery
• tests/gateway/test_ntfy.py — 81 unit tests

Reviewer Feedback Addressed (from #4043)

@TheophileDiot:

• Identity spoofing — removed title field as user identity source. ntfy is now treated as a single trusted channel; user_id is always the topic name. Added test_unknown_publisher_cannot_impersonate_allowed_user test.
• Stale comment — fixed poll=true comment to poll=false
• 401/404 infinite reconnect — added _FatalStreamError exception; 401/404 responses stop the reconnect loop instead of retrying every 60s
• Backoff reset — backoff index resets to 0 when a stream stays alive for ≥60s
• Message truncation — added logger.warning() when message exceeds 4096 char limit
• Config load overhead — check_ntfy_requirements() now reads NTFY_TOPIC env var directly instead of calling load_gateway_config() on every pre-check

@gerrydoro:

• Markdown configurable — set markdown: true under extra: in config.yaml or NTFY_MARKDOWN=true env var; adapter sends X-Markdown: true header. Defaults to false.

How to Test

python3 -m pytest tests/gateway/test_ntfy.py -v

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix
• I've tested on my platform: Ubuntu 24.04 (WSL2)

Documentation & Housekeeping

• No documentation changes needed
• Cross-platform considered — no platform-specific impact