fix(telegram): normalize forum topics and bot command mentions

[nocturnum91]

What does this PR do?

Fixes Telegram gateway group/forum edge cases so General-topic forum messages and bot-command mentions are routed and gated consistently.

Related Issue

N/A.

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

• Normalize Telegram forum General-topic messages so message_thread_id=None maps to thread id "1" where topic routing needs it.
• Fix bot-command mention handling in groups and forum topics.
• Preserve non-forum group reply-derived thread IDs without incorrectly treating them as topic/session routing IDs.
• Update Telegram group/topic gating helpers and regression tests for forum and non-forum behavior.

How to Test

1. Run Telegram gateway focused tests for forum topic normalization and bot-command mentions.
2. Verify General-topic forum messages map to thread id "1" for topic-aware routing.
3. Verify non-forum group replies do not create unintended topic/session routing.
4. Run a read-only Codex review of the final branch delta.

Verification performed during refresh:

• uv run --extra dev pytest ... focused Telegram tests: 104 passed.
• Read-only Codex review: VERDICT: CLEAN.
• Branch was rebased onto current main and updated with --force-with-lease.

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform: macOS

Note: I ran focused/regression tests locally for the changed Telegram gateway behavior and am relying on GitHub Actions for the full matrix.

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — or N/A
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — or N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — or N/A
• I've updated tool descriptions/schemas if I changed tool behavior — or N/A

For New Skills

N/A — this PR does not add a skill.

Screenshots / Logs

N/A. Relevant verification is in local focused test output, Codex review logs, and GitHub Actions checks.

[teknium1]

Merged via #56109 — #56109

Your commit was cherry-picked onto current main with your authorship preserved in git log (merge commit cc1e4c3).

Since this branch was opened, two of the three parts had already landed on main independently:

• the /cmd@botname bot-command mention handling (Telegram bot-menu slash commands (/cmd@botname) dropped in groups with require_mention=true #15415), and
• the forum-topic normalization inside _build_message_event ([Bug]: Telegram DM sends fail with 'Message thread not found' — spurious thread_id from reply chains #3206 / fix(send_message): map Telegram General topic id to None for forum groups #22423).

Telegram also moved from gateway/platforms/telegram.py to plugins/platforms/telegram/adapter.py. The salvage carries the one remaining un-merged delta — your _effective_message_thread_id() helper — and routes both the group gate and the event builder through it, so gating and session routing can no longer diverge (a non-forum reply's anchor id is no longer dropped by ignored_threads or read as a topic under allowed_topics). Regression tests for both cases included. Thanks!